WASHINGTON (NYTIMES) - President Donald Trump's surprise tweet last week that he would pull all US troops from Afghanistan by Christmas is not the only important military mission he may abruptly shrink or end as Election Day nears.

Mr Trump has told senior advisers that he also wants to see plans for withdrawing all US forces in Somalia, despite warnings from senior military and counter-terrorism officials that doing so would bolster the deadly Al-Qaeda affiliate there and cede strategic ground in East Africa to China and Russia.

The President sent mixed signals last month when he declared that US forces "are out of Syria", except to guard the region's oil fields.

His comments came on the day the Pentagon said it was sending Bradley Fighting Vehicles, more fighter jet patrols and about 100 additional troops to north-east Syria after a Russian armoured vehicle rammed a US ground patrol there in August, injuring seven soldiers.

"We're in all these different sites fighting in countries that nobody ever heard of, and it hurts us because we're - you wear out your military," Mr Trump said last week in an interview with Fox Business.

"And we have to be always prepared for China and Russia and these other places. We have to be prepared."

But even senior military commanders have sought to distance themselves from their commander in chief's troop withdrawal forecasts, which have caught them off guard.

And critics say that in seeking to fulfil a campaign pledge to bring US troops home from "endless wars", the President is exposing the country to even greater national security risks.

"There's no strategy; there's just electioneering," said Dr Kori Schake, who directs foreign and defence policy studies at the American Enterprise Institute.

The latest head-snapping news on possible troop withdrawals came this week, when senior administration officials said Mr Trump had told senior aides that he wanted to withdraw US forces from Somalia, confirming an earlier report by Bloomberg News and adding further details.

One idea now under consideration would involve removing most or all ground troops from the country - including those who have been training and advising Somali forces - and ending strikes aimed at combating or degrading Al-Shabaab, Al-Qaeda's largest and most active global affiliate.

Counter-terrorism strikes, drone use, troop presence in nearby countries and targeting individual Al-Shabaab members believed to be plotting terrorist attacks outside Somalia would apparently still be permitted.

The White House convened a small inter-agency meeting of senior officials late last week to discuss Mr Trump's demand for more drastic troop withdrawal options, according to three officials who spoke on the condition of anonymity.

Officials involved in the discussion included Defence Secretary Mark Esper and General Mark Milley, the chairman of the Joint Chiefs of Staff, they said, adding that no decisions had been made.

A Pentagon spokesman referred questions about the deliberations to the White House National Security Council, where a spokesman declined to comment.

There are now about 700 US troops in Somalia. Most are Special Operations forces stationed at a small number of bases across the country.

Their missions include training and advising Somali army and counter-terrorism troops and conducting kill-or-capture raids against Al-Shabaab.

Al-Shabaab has in recent months issued specific new threats against Americans in East Africa - and even in the United States.

After a hiatus this year, it has increased a campaign of car bombings in Somalia, US counter-terrorism and intelligence officials said.

Several ominous signs indicate that Al-Shabaab is seeking to expand its lethal operations well beyond its home base and attack Americans wherever it can - threats that have prompted 46 US drone strikes so far this year to try to snuff out the plotters.

Last year, there were 63 drone strikes, almost all against Al-Shabaab militants, with a few against a branch of the Islamic State in Iraq and Syria (ISIS) group.

In recent years, Al-Shabaab, which US intelligence analysts estimate has 5,000 to 10,000 fighters, has lost many of the cities and villages it once controlled.

Despite a record number of US drone strikes, the group has morphed into a nimbler and deadlier organisation, carrying out large-scale attacks against civilian and military targets across Somalia and in neighbouring countries.

"A withdrawal of US forces from Somalia will give the Shabaab a decisive strategic advantage in the conflict in Somalia and increase the terrorist threat in East Africa, including to Americans and American targets, significantly," said Dr Tricia Bacon, a Somalia specialist at American University in Washington and a former State Department counter-terrorism analyst.

Colonel Christopher Karns, the chief spokesman for the military's Africa Command, declined to comment on Mr Trump's push to withdraw troops from Somalia. Instead, Col Karns offered a defence for the current mission.

"US Africa Command continues to train Somali forces, monitor Al-Shabaab and disrupt and degrade a dangerous Al-Shabaab terrorist network whose long-term ambitions include attacking the United States," he said in a statement.

Col Karns also noted the Pentagon's broader strategy to counter threats globally from Moscow and Beijing.

"When you look at global power competition in Africa, it is very much a place where China and Russia seek to be great and continue to prioritise activity, especially on the economic front," he said.

Even some of Mr Trump's staunchest Republican allies in Congress are warning against deep troop cuts in Somalia.

"This strategy has worked, and our continued presence there has prevented Al-Shabaab from expanding its foothold in the region," Senator James Inhofe, an Oklahoma Republican, the chairman of the Armed Services Committee, said in a statement.

Mr Inhofe expressed hope that Mr Trump would "not take any action that would cause us to lose the ground we've gained, thanks to his strategy".

The military's pushback on large troop pullouts in Somalia came after Gen Milley distanced himself from sudden and conflicting announcements from the White House last week on Afghan troop withdrawals.

With no warning to the Pentagon, Mr Robert O'Brien, the national security adviser, told an audience in Las Vegas on Oct 7 that the US would cut its troops in Afghanistan to 2,500 by early next year.

That surprised Defence Department officials and top military commanders, who said they were still operating under orders to reduce troop levels to 4,500 by later this autumn.

Mr Trump then added to the confusion when he contradicted Mr O'Brien hours later and suggested via Twitter a timeline as early as Christmas to bring all troops home.

"We should have the small remaining number of our BRAVE Men and Women serving in Afghanistan home by Christmas!" he wrote.

Gen Milley, wary of upsetting the good working relationship he has established with the President, nonetheless appeared to voice frustration with the accelerated timeline and the conflicting troop withdrawal messages.

He did not criticise the commander in chief, but he discussed the national security adviser's comments.

"I think that Robert O'Brien or anyone else can speculate as they see fit," Gen Milley said in an interview with NPR on Sunday (Oct 11).

"I'm going to engage in the rigorous analysis of the situation based on the conditions and the plans that I am aware of and my conversations with the President."

In north-east Syria, the military's Central Command sent reinforcements to the hotly contested region last month after the Russians deliberately rammed the US vehicle.

White House and Pentagon officials criticised the Russians for what US officials said was reckless aggression.

But Mr Trump kept silent on the episode, prompting Democrats to seize on it as the latest example of the President's failure to challenge Russia's increasing hostility toward the West, which also includes interfering in the election and putting bounties on US troops in Afghanistan.

Former vice-president Joe Biden, the Democratic presidential nominee, rebuked Mr Trump for failing to publicly address the altercation in Syria.

"Did you hear the President say a single word? Did he lift one finger?" he said in a speech in Pennsylvania on Aug 31.

US military commanders voiced cautious optimism that the President would not pull out any of the more than 600 troops in Syria, at least for now.

Those troops are helping Syrian Kurdish allies carry out counter-terrorism missions against remnants of ISIS.

But those same commanders remember all too vividly Mr Trump's penchant for taking to Twitter to blurt out a new policy change, as he did in announcing a previous troop withdrawal from Syria in 2018 without informing the Pentagon. That move prompted Mr James Mattis to resign as defence secretary.

With Election Day less than three weeks away, Pentagon officials are bracing to deal with the consequences of another possible presidential troop forecast.

"How will we mitigate the risk of withdrawing US troops from these places?" said Dr Seth Jones, the director of the transnational threats project at the Centre for Strategic and International Studies, a Washington think tank.

"I'm hearing crickets. That is not a recipe for a sound foreign policy."