US Defence Secretary Robert Gates has praised the "valour and sacrifice" of Nato allies in Afghanistan, a day after being quoted as questioning them.
Robert Gates said Nato was "taking the fight to the enemy"
Mr Gates said quotes attributed to him in the Los Angeles Times criticising allies' counter-insurgency skills did "not reflect reality".
He said his concern about such skills was directed at the alliance as a whole and not other member nations.
The Nato-led force has almost 37,000 troops in Afghanistan.
This week the US announced it was sending another 3,200 American soldiers to Afghanistan to add to its 26,000 already there. About half serve under the Nato-led International Security Assistance Force.
However Mr Gates said at a Pentagon briefing that the latest deployment did not reflect US dissatisfaction at allies' performance.
"Allied forces from the United Kingdom, Canada, the Netherlands, Australia and Denmark and other nations have stepped up to the plate and are paying a significant and powerful role in Afghanistan," he said.
Mr Gates said the quotes in the LA Times did "not reflect reality or, I believe, the views of our governments".
The BBC's Vincent Dowd in Washington says it was clear Mr Gates wanted to smooth over annoyance created within Nato.
One British MP, Patrick Mercer, had called the quotes "bloody outrageous".
The Dutch defence ministry called in the US ambassador to query the comments.
The Dutch later expressed satisfaction with Mr Gates's explanation that he had been misquoted.
Mr Gates said Nato had "rolled back the Taleban from previous strongholds in the south. They are taking the fight to the enemy in some of the most gruelling conditions imaginable".