Britain will keep its current level of 450 troops on non-combat missions in Afghanistan through 2016, Defence Secretary Michael Fallon said in a written statement to parliament on Tuesday.

The announcement comes after the United States earlier this month announced that thousands of its troops would stay in Afghanistan longer than promised following intense recent fighting.

"Both the US and our own decisions underline NATO's continued commitment to training and assisting Afghan forces as they grow stronger," Fallon said.

"We have now concluded that we should maintain the scale of the UK's current military mission in the country in 2016, to help build a secure and stable Afghanistan," he added.

Fallon explained that British troops were involved in training Afghan army officers, building capacity in Afghan security ministries and supporting NATO operations in Kabul.

Afghan President Ashraf Ghani welcomed Britain's announcement.

International help for the Afghan army "augments the commitment and effectiveness of these forces to fulfil their grand mission, and further boosts their morale," he said in a statement.

"The government of Afghanistan thanks its international partners like Britain for their assistance," he said.

The last British combat troops in Afghanistan were airlifted out of Camp Bastion, a sprawling base located in the southern Helmand province, last October.

The pull-out formally ended a mission that lasted longer than World War II and cost 453 lives.

Britain had previously said it would keep non-combat troops in Kabul through 2015 at least.

President Barack Obama has said the US will maintain its current force of 9,800 in the country through 2016, going back on a campaign promise to end the war in Afghanistan after acknowledging that Afghan forces were not ready to stand alone.

After that, rather than go down to a normal embassy presence as had been planned, the United States will leave a force of 5,500 troops in place to train Afghan forces and conduct counter-terrorism missions.

US-backed forces ousted the Taliban government from Kabul in 2001. At the height of its deployment, US had around 100,000 troops in Afghanistan.

Emboldened by their recent three-day occupation of Kunduz, the first Afghan city to fall to the Taliban since their 2001 ouster from power, insurgents have made brazen attempts to overrun several other provincial centres in recent weeks.

Obama and Pakistani Prime Minister Nawaz Sharif last week issued a joint call for the Taliban to return to peace negotiations with the Afghan government.