(Adds announced committee hearings; updates share prices)
By Susan Cornwell
WASHINGTON, Sept 18 (Reuters) - Democratic leaders in the U.S. Congress on Monday demanded that lawmakers wait to find out the budgetary and healthcare impacts of a new, last-ditch legislative effort by Republicans to repeal Obamacare before voting on it.
In their long-running war on former President Barack Obama's signature healthcare law, Senate Republicans are now proposing to replace it with a system that would give states money in block grants to run their own healthcare programs.
Drafted by Republican Senators Lindsey Graham and Bill Cassidy, the bill was introduced last week. Graham and Cassidy said they were close to securing the votes needed for passage, but the bill's outlook was uncertain.
If approved, it would replace the 2010 Affordable Care Act, known informally as Obamacare, which Republicans have long seen as government overreach into the healthcare business.
The Graham-Cassidy measure has revived a fight that many in Washington thought was over when an Obamacare repeal-and-replace bill flopped in the Senate in July, humiliating Republican Senate Majority Leader Mitch McConnell and President Donald Trump.
Two Senate committees, including the powerful Finance Committee, on Monday announced they would hold hearings on the bill next week, the first public hearings all year for any Republican Senate proposal to overhaul Obamacare.
Republican Senator John McCain had called for a return to regular order and public hearings before voting against a repeal-and-replace bill in July. Senator Ron Wyden, the top-ranking Democrat on the Finance Committee hearing, said next week's hearing "makes a mockery of regular order."
The Congressional Budget Office, a non-partisan fiscal analysis unit of Congress, said on Monday it will make a preliminary assessment of the bill's impact next week. But it said it will not be able to estimate the impact on the deficit or changes in insurance coverage or premiums for several weeks.
Worried Democrats seized on the statement to urge Republicans to wait for a full CBO score before holding a vote.
"Have the courage and decency to wait for a CBO score," Senate Democratic leader Chuck Schumer said on the Senate floor on Monday.
The House of Representatives is on a break this week.
A delay to wait for a CBO analysis is something Republicans can ill afford since in two weeks Senate procedural rules will make it much more difficult for them to advance the legislation.
A special parliamentary procedure that would allow the bill to move forward in the Senate with a simple majority of only 51 votes will expire in two weeks. After that, it would need 60 votes, like most Senate legislation. Republicans have a slim 52-vote Senate majority.