The US Defence Secretary, Robert Gates, has arrived in Afghanistan, ahead of the thousands of new troops announced by Barack Obama.
The Pentagon gave orders for 16,000 to deploy, the first wave of the 30,000 decided by the American president last week.
Gates said his message is that the US is “in this thing to win”.
He has held talks with Afghan President Hamid Karzai, who was re-elected in August amid allegations of rampant fraud.
Gates said he pressed Karzai to appoint “honest and capable” ministers in his new cabinet.
The new troops will nearly double the US marine contingent in the south of Afghanistan. But the surge will be shortlived, Obama has said the US will start to withdraw by 2011.
Gates, however, is likely to assure Kabul that this will depend on the situation on the ground at the time.
Karzai has said that without US help, Afghanistan will not be able to maintain its army and police for at least the next 15 to 20 years.