WASHINGTON (AP) — The Republican-led Senate is poised to take a step forward on dismantling President Barack Obama's health care law despite anxiety among GOP lawmakers over the lack of an alternative.

Senate approval — expected late Wednesday or early Thursday — and then House passage would trigger committee action to write repeal legislation that could come to a vote next month. A full replacement would follow sometime after that, presuming Republicans can come up with one.

"We must act quickly to bring relief to the American people," said Senate Majority Leader Mitch McConnell, R-Ky.

President-elect Donald Trump said Wednesday that repealing and replacing the law should happen "essentially simultaneously," even in the same day, week or hour. That will be almost impossible to achieve due to complex Senate rules, united Democratic opposition and substantive policy disagreements among Republicans.

Republicans plan to get legislation voiding Obama's law and replacing parts of it to Trump by the end of February, House Majority Leader Kevin McCarthy, R-Calif., said Wednesday on "The Hugh Hewitt Show," a conservative radio program. Other Republicans have said they expect the process to take longer.

The 2010 law extended health insurance to some 20 million Americans, prevented insurers from denying coverage for pre-existing conditions and steered billions of dollars to states for the Medicaid health program for the poor.

The Senate procedural vote will set up special budget rules that will allow the repeal vote to take place with a simple majority in the 100-member Senate, instead of the 60 votes required to move most legislation.

That means Republicans, who control 52 seats, can push through repeal legislation without Democratic cooperation. They're also discussing whether there are some elements of a replacement bill that could get through at the same time with a simple majority. But for most elements of a new health care law, Republicans are likely to need 60 votes and Democratic support, and at this point the two parties aren't even talking.

Increasing numbers of Republicans have expressed anxiety over obliterating the law without a replacement to show voters.

Sen. Susan Collins, R-Maine, said she wants to at least see "a detailed framework" of a GOP alternative health care plan before voting on repeal. She said Republicans would risk "people falling through the cracks or causing turmoil in insurance markets" if lawmakers voided Obama's statute without a replacement in hand.

House leaders planned a Friday vote on the budget, though Republicans in that chamber also had misgivings.

Many members of the conservative House Freedom Caucus were insisting on first learning details about what a GOP substitute would look like.

They also were demanding that once a future repeal bill becomes law, it should take no longer than two years to take effect. Some GOP senators have discussed a phase-in of three years or longer to give lawmakers more time to replace Obama's overhaul and make sure people now covered by that law can adjust to a new program.

"There's more elections and more uncertainty," Rep. Dave Brat, R-Va., a Freedom Caucus member, said of his objections to a longer transition period.

Some more moderate Republicans were unhappy, including Rep. Tom MacArthur, R-N.J., a leader of the House Tuesday Group of GOP centrists. He said he would oppose the budget because there was too little information about the replacement, including whether people receiving expanded Medicaid coverage or health care subsidies under the existing law would be protected.

"We're loading a gun here. I want to know where it's pointed before we start the process," MacArthur said.