LONDON - British Prime Minister Gordon Brown is optimistic other allies will send more troops to Afghanistan, backing up an expected sharp increase in U.S. forces, according to a letter to NATO released on Wednesday.

U.S. President Barack Obama, who vowed on Tuesday to finish the job in Afghanistan, could announce an increase of around 30,000 troops next week, U.S. officials say.

Britain, which is prepared to commit an extra 500 troops, has been trying to persuade other countries in the NATO-led coalition to send around another 5,000 soldiers to help share the burden of combat and train Afghan forces.

In the last week, I have asked my ministers and senior officials to pursue this effort with 10 key coalition partners, focusing on increased troop commitments in the New Year, Brown said in a letter to NATO Secretary-General Anders Fogh Rasmussen.

Following these meetings and contacts, I am now optimistic that a majority of these countries will indeed make available increased numbers of troops, and more police trainers and civilian support, he added in the letter, sent on Tuesday.

Brown's spokesman did not say which countries were expected to supply extra troops but said they all already had forces in Afghanistan.

DECISIONS ON HOLD

Many NATO members have put on hold their own decisions on sending extra forces until Obama's announcement, expected since General Stanley McChrystal, the top U.S. and NATO commander in Afghanistan, recommended an extra 40,000 U.S. troops in August.

I believe that next week we will see the American government and the rest of NATO coming together in a strategy that will mean we will have the forces that are necessary so we can create the space for a political solution in Afghanistan, Brown told parliament on Wednesday.

British Defense Secretary Bob Ainsworth said on Tuesday that the wait for Obama's decision had been a period of hiatus that had made it harder to maintain public support for the Afghan mission after 98 British military deaths this year.

NATO forces, engaged in some of the fiercest fighting this year since the 2001 U.S.-led invasion, hope in the long term to transfer security responsibility to bigger and better-trained Afghan army and police forces to enable them to withdraw.

NATO will meet on December 7 to raise more forces for its Afghan mission, which currently involves 65,000 U.S. troops and 39,000 from allied nations, including 9,000 from Britain.

Brown told Rasmussen he would invite key allies in the Afghan coalition to London in January to discuss a timetable for district-by-district handover of security to Afghan control.

(Editing by Adrian Croft)

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