Foreign Secretary David Miliband has welcomed US plans to send 17,000 more troops to Afghanistan.
Some of the US troops will be deployed in Helmand province, where British and Taleban forces have been involved in fierce fighting.
Mr Miliband, who is visiting British forces in Afghanistan, said the UK had not received a request for more troops.
Britain had no plans to increase its troop numbers beyond the 9,000 already stationed in the country, he added.
Mr Miliband said: "I think that there is a universal recognition that these extra American troops can play, and will play, an important and positive role, when they are aligned and allied with a strategy for economic development and political development.
"In terms of the United Kingdom we represent about 12% of the troops in Afghanistan at the moment. We have had no request to increase our number of troops but of course we always keep the number under review."
Mr Miliband flew into Afghanistan as the British death toll in the country continued to rise.
He visited military and civilian staff and held talks with Afghan leaders, including the governor of Helmand, Gulab Mangal, about the fight against the Taleban and the progress of local development.
Last week, Mr Miliband acknowledged that the Taleban's use of terror tactics had created a "strategic stalemate" in parts of the country.
His visit came as the number of British deaths in the Afghan conflict since 2001 grew to 145.
A soldier from 1st Battalion The Rifles died after coming under fire on a foot patrol south of Lashkar Gah in Helmand.
He was the eighth British serviceman to die in Afghanistan so far this year.
The Foreign Office said Mr Miliband's visit was an opportunity for him to exchange "details and views" with the Afghan government on the military and construction efforts.
"He is keeping abreast of that," a spokesman said. "It is all part of an ongoing discussion with the Afghan government."
US President Barack Obama said the 17,000 extra US troops had been due to go to Iraq but were being redirected to "meet urgent security needs".
It is the first major military decision by the Obama administration, and comes amid a major review of US policy in Afghanistan and Pakistan.
The additional troops are to be sent before warmer weather brings an expected increase in fighting in Afghanistan, US defence officials said.
They will be made up of 8,000 marines, and 4,000 army soldiers, plus another 5,000 support staff. They will serve in the south.
Afghan defence ministry spokesman Mohammad Ishaq Payman told the AFP news agency that the move was a "positive development".
"But we have our own conditions. We want these troops to be deployed in areas where they could play a positive role in suppressing terrorists," he said.
"We want them to be deployed along the border, in eastern, south-eastern and southern parts of the country."