(Recasts, adds details on House letters)

By David Lawder

WASHINGTON, Nov 12 (Reuters) - A growing number of Republicans in Congress want to use government spending bills as leverage to prevent President Barack Obama from taking unilateral action to ease U.S. immigration policies.

Senator Jeff Sessions, poised to lead the Senate Budget Committee next year, on Wednesday called on his fellow Republicans to press for a short-term spending bill extension into early next year and withhold funds needed to implement any "unlawful amnesty" for undocumented immigrants ordered by Obama.

He told reporters that a short-term extension into next year would allow a new Republican majority in the Senate to cut spending and be in a position to use spending bills to prevent Obama from issuing visas and identification cards to such immigrants.

A short-term extension "would be smart for a whole lot of reasons," Sessions said. "Senator Reid shouldn't be entitled to bind the country next year when we've got a new Congress," he said, referring to Senate Democratic leader Harry Reid.

Meanwhile, more than 50 House Republicans have signed a letter circulated by conservative Representative Matt Salmon, calling for a pre-emptive strike to bar from spending legislation any use of federal money to legalize undocumented immigrants. Salmon plans to send the letter to House Republican leaders on Thursday, his spokesman said.

The House and Senate Appropriations committees are negotiating a $1 trillion "omnibus" spending package that would keep the government funded through Sept. 30, 2015. Congress must pass new spending legislation by Dec. 11 to avoid a government shutdown.

The warnings over immigration funding were reminiscent of Republicans' zeal to de-fund Obama's health care reform law in 2013, which led to a 16-day shutdown of federal agencies last year.

House Republican leaders have previously favored a longer-term spending bill that would allow them to concentrate on other issues next year. But House Majority Leader Kevin McCarthy said he would listen to members.

"We'll get together as a conference and all decide," McCarthy told reporters.

Sessions said a Republican Congress next year could act to deny funding for the implementation of any executive order Republicans oppose.

"If Congress disapproves of the president providing ID cards and all that for people who've been in the country illegally, they should not appropriate the money to fund it." (Reporting By David Lawder; Editing by David Gregorio and Ken Wills)