The Government has welcomed Barack Obama's commitment to keep thousands of US troops in Afghanistan.
The US President has announced plans to keep nearly 10,000 troops in Afghanistan through most of next year and 5,500 when he leaves office in 2017.
Mr Obama had previously promised to end the war during his term in office, with only a small force based in the Embassy beyond 2016.
He called the new war plan a "modest but meaningful" extension of the US military mission in Afghanistan.
A UK Government spokesman said: "We welcome the announcement that the US will maintain its current military footprint in Afghanistan into 2016. It sends a clear message of enduring commitment to the Afghan Government and to Afghanistan's long term security.
"The UK is committed to promoting Afghanistan's stability and prosperity through our financial, political and military assistance, which includes contributing to the development of future Afghan leaders at the officer academy in Kabul and delivering a vital role for Nato's Resolute Support Mission HQ."
Explaining his U-turn, Mr Obama said that while Afghan forces have made progress, the security situation in the country remains fragile.
The US will maintain the current force of 9,800 troops in Afghanistan through most of next year, then draw down to 5,500 troops in 2017, at a pace still to be determined after consultation with commanders.
It will be up to Mr Obama's successor - the third president to oversee the US presence in Afghanistan - to decide how to proceed from there.
"I suspect that we will continue to evaluate this going forward, as will the next president," Mr Obama said.
The decision is likely to make Afghanistan a major issue in the Democrat and Republican campaigns for the White House.