WASHINGTON (REUTERS) - US President Donald Trump's decision to cut US troop levels in Germany blindsided a number of senior national security officials, according to five sources familiar with the matter, and the Pentagon had yet to receive a formal order to carry it out, Reuters has learned.

Mr Trump decided to remove 9,500 troops from Germany, one of America's strongest allies, reducing the number there to 25,000 from 34,500, a senior US official said on Friday (June 5).

That official said it was the result of months of work by the US military leadership and had nothing to do with tensions between Mr Trump and German Chancellor Angela Merkel, who thwarted his plan to host an in-person Group of Seven (G-7) summit this month.

But other sources familiar with the matter said a number of US officials at the White House, State Department and Pentagon were surprised by the decision and they offered explanations ranging from Mr Trump's pique over the G-7 to the influence of Mr Richard Grenell, the former US ambassador to Germany and a Trump loyalist.

Reuters could not determine if Mr Grenell had played a direct role with Mr Trump in the decision-making. Mr Grenell resigned his post on June 1, according to a State Department spokeswoman.

The Defence and State Departments referred questions to the White House National Security Council, which declined comment.

'ALL GOSSIP'

Asked for comment, Mr Grenell said that "this is all gossip"and declined to address specific questions about the decision and his role in it. The reduction, he said, had been "in the works since last year".

He underscored US frustration over Germany's failure to meet a NATO target of defence spending of 2 per cent of GDP. He noted that NATO Secretary General Jens Stoltenberg named Germany as the only country that had not submitted a credible plan for how to reach their commitment.

At an online event hosted by the Atlantic Council think tank on Monday, Mr Stoltenberg declined to comment on what he termed "media leakages and media speculation" when asked about US plans to cut troop numbers in Germany.

He said NATO was "constantly consulting with the United States, with other NATO allies on the military posture, presence in Europe".

Speaking on condition of anonymity, a US official told Reuters the Pentagon had not received a formal order to cut troops and that the decision caught some Defence Department officials off guard and scrambling to figure out its meaning and impact on relations with Germany.

Germany was not consulted before the decision was first reported by the Wall Street Journal on Friday, two sources familiar with the matter said.

German government officials said on Monday that Berlin had not received confirmation of the US move.

But Mr Peter Beyer, the German coordinator for transatlantic ties, said it would "shake the pillars of the transatlantic relationship".

The Trump administration pushed to reduce US troops in Germany for years and Mr Grenell has criticised Berlin in public and private for failing to meet the NATO target of spending 2 per cent of GDP on defence, said a source briefed on US-German military relations.

"In that sense, it wasn't a surprise, but there was no consultation or coordination. And Trump administration officials had said they did not expect a withdrawal of forces," the source added.

The decision - which has not been officially confirmed by the White House - also surprised a number of senior national security officials in the US government.

Senior State Department, Pentagon and some national security council officials were blindsided and "learned something was up when calls started coming around and the WSJ article hit", said a third source familiar with the matter.

'NOT PLAYING BALL'

A US military drawdown from Germany could sharpen trans-Atlantic tensions that Trump has fuelled by questioning the value of NATO and criticising some alliance members' defence spending.

Security experts have called the withdrawal plan a "gift" to Russia as it comes amid serious tensions between Washington and Moscow over arms control, Moscow's support for separatists in Ukraine, the US withdrawal from the Iran nuclear deal and other issues.

But current and former officials noted the Trump administration had at times announced steps - such as the total withdrawal of US troops from Syria in 2018 or an immediate US$1 billion (S$1.4 billion) cut in US funding for Afghanistan in March - that did not come to pass.

A congressional aide familiar with the matter said he was told Mr Trump's decision was motivated, in part, by Mrs Merkel's reluctance to attend the US G-7 summit because of the coronavirus pandemic.

"This was originally only done at very high levels and he (Grenell) was involved. This was kept extremely close hold," said the congressional aide on condition of anonymity, saying he was told the decision was "sped up because he (Trump) was mad at Merkel for cancelling his G7 party because of Covid."

US Ambassador to Poland Georgette Mosbacher and Mr Grenell publicly warned in August that Mr Trump could withdraw some troops from Germany and suggested they could be relocated to Poland unless Ms Merkel responded to Mr Trump's calls to increase defence spending.

"It would be the ultimate kind of slap to Germany if they were rotated out of Germany and into Poland," said a former senior US official familiar with the matter, who requested anonymity in order to speak freely.

"From their (Grenell's and Mosbacher's) point of view, the Germans were not playing ball and should be punished."