BRUSSELS (REUTERS) - Nato allies are set to agree on Thursday (Nov 9) to increase by some 3,000 personnel the troop levels for the alliance's Afghanistan training mission, Nato Secretary-General Jens Stoltenberg said.

About half the additional troops will come from the United States and the other half from non-US Nato allies and partner countries, Mr Stoltenberg said.

"We have decided to increase the number of troops... to help the Afghans break the stalemate," Mr Stoltenberg told a news conference on Tuesday before a meeting of the alliance's defence ministers later this week.

Mr Stoltenberg stressed that the soldiers would not have combat roles but would be part of Nato's train, advise and assist mission called Resolute Support.

US Army General John Nicholson, the commander of the Resolute Support mission and of US forces in Afghanistan, called for more troops in February, saying that a few thousand more troops would make a difference in weakening the Taleban and other Islamist militants.

The Nato contribution would take Resolute Support, which is building up Afghanistan's army and air force, to around 16,000 troops, up from around 13,000 today, Mr Stoltenberg said.

Under a new strategy announced by US President Donald Trump, US Defence Secretary James Mattis said in September that more than 3,000 additional US troops would be deployed to Afghanistan.

While Nato officials declined to discuss troop numbers in detail, the expected announcement on Thursday by Nato defence ministers is likely to mean the US troops will be split between the training mission and the US-led counter-terrorism mission in Afghanistan.