WASHINGTON (Reuters) - Democratic leaders in the U.S. Congress on Monday demanded that legislative analysts examine both the budgetary and healthcare impacts of a last-ditch effort by Republicans to repeal Obamacare.

In a long-running war on former President Barack Obama’s signature healthcare law, Republicans face a two-week countdown before Senate procedural rules make it much harder for them to advance their latest bill.

Republican Senators Lindsey Graham and Bill Cassidy propose replacing the 2010 Affordable Care Act, known informally as Obamacare, with a plan to give U.S. states money in the form of block grants to run their own healthcare programs.

Democrats warned that the bill would be very costly for some states and urged the Congressional Budget Office (CBO) to study more than the measure’s effect on the federal budget.

“A comprehensive CBO analysis is essential before Republicans force a hasty, dangerous vote on what is an extreme and destructive repeal bill,” senior congressional Democrats Chuck Schumer, Nancy Pelosi, Bernie Sanders and others, said in a statement.

Past attempts by Republicans to gut Obamacare have been hampered, in part, by CBO estimates that showed the bills would have left millions more Americans without health insurance.

President Donald Trump has been telephoning members of Congress in recent days urging action on dismantling Obamacare.

Previous attempts by Republicans to do that met with humiliating failure in July, when an Obamacare repeal-and-replace bill flopped in the Senate, triggering a barrage of hectoring tweets from Trump against party leaders.

Now Graham and Cassidy have just two weeks left to act, under a special parliamentary procedure that would allow their bill to advance in the Senate with 51 votes, instead of the 60 votes that most Senate legislation needs to win approval

“We are two votes short,” Graham said in a weekend interview with Breitbart News.

White House counselor Kellyanne Conway told Fox News’ “Fox and Friends” that the 11th-hour effort “is gaining in support.”

Senate Republican Leader Mitch McConnell has not promised to bring the bill to the floor for a vote. But he has asked the CBO, a non-partisan scorekeeper, for a quick assessment of the measure, which could pave the way for a vote.

Not all the Senate’s conservatives back the bill. Senator Rand Paul said it did not go far enough to repeal Obamacare.

But if it can get through the Senate, it may have a chance in the House of Representatives, also run by Republicans. House Speaker Paul Ryan last week tweeted his appreciation to Graham and Cassidy and some members of the Freedom Caucus conservative group have praised the bill.

Obama’s healthcare reform provided health benefits to 20 million Americans. Since its passage, Republicans have sought to undermine it, calling it government overreach.

But the party has failed to repeal Obamacare or enact a replacement system, despite controlling the Senate, the House and the White House since the November 2016 elections.

Negotiations were continuing on a separate bipartisan Senate effort to repair Obamacare without repealing it, with the differences narrowing between the two sides, a spokeswoman for Democratic Senator Patty Murray said. Murray and Republican Lamar Alexander are working on a plan to protect subsidies that are paid to insurance companies to help offset discounts under Obamacare.