Nato nations today pledged an extra 7,000 troops for Afghanistan as the US secretary of state, Hillary Clinton, in Europe to drum up more military support for the campaign, acknowledged that America was becoming "weary of war".

At least 25 nations would provide the additional forces from next year, "with more to come", the Nato secretary general, Anders Fogh Rasmussen, told reporters after talks with Clinton.

"The strongest message in the room today was solidarity," Rasmussen said. "Nations are backing up their words with deeds."

Clinton is in Brussels to press Washington's allies in Afghanistan to commit more troops, particularly combat forces, after Barack Obama's decision to send 30,000 more American soldiers to Afghanistan. She was due later to have separate discussions with ministers from countries within and outside Nato.

Citing Obama's promise to begin withdrawing US forces in July 2011, Clinton said that while the need for the extra forces was immediate, "their presence will not be indefinite".

She acknowledged the human toll exacted on troops from both the US and their allies in Afghanistan and elsewhere in recent years. "Today, our people are weary of war," she said. "But we cannot ignore reality. The extremists continue to target innocent people and sow destruction across continents. From the remote mountains of Afghanistan and Pakistan, they plot future attacks. As secretary general Rasmussen said earlier this week, 'This is our fight, together.' And we must finish it together."

Addressing the North Atlantic Council, Nato's highest political body, Clinton said that eventual troop withdrawal was dependent on a gradual transfer of responsibility to Afghan security forces.

"The pace, size, and scope of the drawdown will be predicated on the situation on the ground," she said. "If things are going well, a larger number of forces could be removed from more areas. If not, the size and speed of the drawdown will be adjusted accordingly."

The US has about 71,000 troops in the country, as against about 38,000 sent by 42 other Nato and non-Nato nations.

The foreign secretary, David Miliband, also asked Nato members today to lend their support to efforts to bring peace to Afghanistan.

"We all know that in the 1990s, Afghanistan was the incubator of international terrorism, the incubator of choice for global jihad," he said. "The badlands of the Afghan-Pakistan border are a threat to people everywhere, whatever their religion, and that's why it's very important that we make progress."

Also in Brussels was General Stanley McChrystal, the top US commander in Afghanistan and the main proponent of a "surge" strategy in the country, who was to explain the state of the mission to Nato's main political council.

Before Clinton left, there was a degree of scepticism in America over the extent of help the US would receive, whatever the Nato promises.

Professor Eliot Cohen, a former state department adviser, spelled out in today's Wall Street Journal criticism of US allies often heard around Washington when he predicted that the Nato figures would be achieved "only by accounting tricks". He wrote: "The Europeans have repeatedly revealed their aversion to combat."