U.S. Defence Secretary Robert Gates will consider a proposal to send some 3,000 additional U.S. troops to Afghanistan to thwart any spring offensive by Taliban militants, the Pentagon said on Wednesday.

"This proposal is coming before the secretary this week," Pentagon press secretary Geoff Morrell said.

"He will take it and consider it thoroughly before approving it," Morrell told reporters.

The troops would be provided by the U.S. Marine Corps, he said.

Morrell said the proposal, which had been developed by the Pentagon's Joint Staff, would involve the extra Marines deploying to southern Afghanistan, where fighting between the Taliban and NATO-led forces has been most intense.

The United States currently has some 27,000 troops in Afghanistan. Around half form part of a NATO-led security assistance force while the remainder conduct missions ranging from counter-terrorism to training Afghan troops.

"The idea is to get this in place to prevent, as we did last spring, another attempt by the Taliban to come back," Morrell said. "The timing is that they would be in place by April. This is a one-time seven-month deployment."