U.S. eyes Pakistan assistance after Times Square plot

But Gates appeared to play down the chances of an expanded crackdown by Pakistan because of the strain its security forces are already under battling militants in tribal areas bordering Afghanistan.

"We're willing to do as much with the Pakistanis and for the Pakistanis as they are willing to accept," Gates said. "It's their country. They remain in the driver seat. They've got their foot on the accelerator."

Investigations into the Pakistani-born suspect in the bomb attempt in New York's Times Square on Saturday have uncovered possible links to the Pakistani Taliban and a Kashmiri Islamist group.

That has prompted speculation that the United States, Pakistan's top provider of aid, could press Islamabad to open risky new fronts against Islamic militants.

But Gates, far from publicly calling on Pakistan to do more, renewed praise of Islamabad's efforts against insurgents and acknowledged that Pakistan's armed forces were already stretched.

"The Pakistanis have been doing so much more than any of us would have expected 18 months or two years ago," Gates said.

"You also have to realise that, with their military operations in the West, they've started to be pretty thinly stretched themselves, as well as taking a substantial number of casualties."

The United States, which sees Pakistan's effort against militants as crucial to its fight against the Taliban in Afghanistan, has about 200 military personnel in Pakistan, including Special Operations forces on a training mission.

The CIA is also waging a covert war using pilotless drone aircraft to target insurgents in Pakistan.

"I think cooperation has continued to (improve), the relationship is continuing to improve, and I think we just keep moving in that direction," Gates said.

(Reporting by Adam Entous; Editing by Anthony Boadle)