(Fixing typo in headline)
By Susan Cornwell and David Morgan
WASHINGTON, March 17 (Reuters) - U.S. President Donald Trump on Friday stepped up his fight for support on Republicans' plan to dismantle Obamacare, wooing some conservative lawmakers at the White House while legislation advanced toward a possible vote in the House of Representatives next week.
Republicans remain deeply divided over their U.S. healthcare overhaul, Trump's first major legislative initiative and one that aims to make good on his campaign pledge to repeal and replace the healthcare plan put in place by his Democratic predecessor, Barack Obama.
Trump met at the White House on Friday with 13 members of the House Republican Study Committee, a large group of conservative lawmakers seeking changes to Medicaid, the joint federal-state health insurance program for the poor.
"I'm 100 percent behind this," Trump told reporters after the meeting.
Trump said all the lawmakers in attendance now supported the healthcare bill after previously questioning it.
"We made certain changes but frankly very little," he said.
U.S. Health Secretary Tom Price also did his part to win over reluctant Republican lawmakers in a meeting at the Capitol.
The healthcare measure championed by House Speaker Paul Ryan passed through a key House panel on Thursday despite objections by some conservatives who consider it too similar to the 2010 law that became known as Obamacare.
The Republicans' proposed replacement plan still faces a battle in the full House and then the Senate, despite efforts by the White House and Republican leaders to satisfy conservative opponents who are pushing for several changes.
Democrats have roundly rejected the Republicans proposal, saying it harms the poor, elderly and working families while offering tax cuts to rich Americans and companies.
Price told reporters on Friday the proposal addressed several issues important to Trump, such as maintaining insurance coverage of patients with pre-existing medical conditions.
"The president's very supportive of this plan, thinks that it addresses his priorities," Price said at a news conference ahead of a meeting with House Republicans to help coalesce support.
Without Democratic support, Republicans cannot afford to lose many votes from their own ranks, even though they control both chambers of Congress, as well as the White House.
Conservatives have criticized the legislation as too similar to Obama's law. Some have said they want a quicker end to Obamacare's expansion of Medicaid, while others are concerned about insurance costs for consumers.
Representative Mark Meadows, chairman of the conservative House Freedom Caucus, wants changes in private insurance mandates that he says will lower healthcare premiums.
But after Friday's meeting with Price, he expressed frustration there were no commitments from leadership on any changes except a possible optional work requirement on Medicaid, which "doesn't move the ball more than a couple yards on a very long playing field."
He said his group has spoken with Senate Republicans about potential changes and will propose an amendment on Monday.
Several Senate Republicans also have said they would reject the measure in its current form.
Obamacare expanded insurance to about 20 million Americans but the nonpartisan Congressional Budget Office said on Monday that 14 million Americans would lose medical insurance by next year under the Republican plan.
The CBO projected 52 million people would be uninsured by 2026 if the bill became law, compared with 28 million who would not have coverage that year if the law remained unchanged.
Additional reporting by David Morgan; Writing by Susan Heavey; Editing by Bill Trott