A growing number of Republicans in the US Congress want to use government spending bills as leverage to prevent US President Barack Obama from taking unilateral action to ease the country's immigration policies.

Senator Jeff Sessions, poised to lead the Senate Budget Committee next year, called on his fellow Republicans on Wednesday to press for a short-term spending bill extension into early next year and withhold funds necessary to implement any "unlawful amnesty" that Obama might order for immigrants who entered the US illegally.

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.

The White House said Obama is nearing a final decision on what executive actions he'll take on immigration.

Obama has pledged to act on immigration before the end of the year.

Immigration activists want Obama to halt deportations for millions. White House spokes-man Josh Earnest said Obama still hasn't decided what actions he'll take.

Earnest said Obama has been discussing options with Cabinet officials. Final recommendations are expected after Obama returns from Australia on Sunday.

Earnest also said that if the US House were to later pass a Senate-passed immigration bill, Obama would sign it in a way that supersedes his executive actions.

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 that calls for a preemptive strike to bar from spending legislation any use of federal money to legalize the immigration of those who entered the country illegally. 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 defund Obama's health care reform law in 2013, which led to a 16-day shutdown of federal agencies.

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 will listen tomembers.

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

Reuters - AP