WASHINGTON - In a possible breakthrough for US Republicans' effort to roll back Obamacare, the House of Representatives plans to hold a vote Thursday on compromise legislation, potentially ending a logjam that has delayed advancing US President Donald Trump's campaign promise to repeal the law.

The decision to hold a vote comes after key moderate lawmakers met with Trump on Wednesday and said a revised bill might win approval as conservatives voiced no objections.

House Majority Leader Kevin McCarthy said Republican leadership is confident there is enough support for the bill to pass.

Keen to score his first major legislative win since taking office in January, Trump has been personally engaged in building support among fellow Republicans in the House for an effort that has already twice collapsed.

Aides said Trump has been furiously working the phones, trying to make good on a key promise to voters: overhauling former president Barack Obama's signature domestic legislation. The effort is showing Trump how hard it is to manage factions among the Republicans, who control both chambers of Congress.

The House bill has been changed several times as Republicans have tried to balance demands by conservatives for a maximum Obamacare rollback with moderates' worries about angering voters who like parts of the law, formally known as the Affordable Care Act and enacted in 2010.

One popular feature of the law lets young people stay on their parents' plans until age 26; another protects people with pre-existing health conditions, a provision defended by late-night talk show host Jimmy Kimmel, who tearfully revealed on Monday his newborn son had a congenital heart condition.

Kimmel's monologue has been viewed nearly 19 million times on his show's Facebook page, and on Wednesday morning was the No. 1 trending story on YouTube.

Trump met at the White House with two key House Republican moderates, Michigan's Fred Upton and Missouri's Billy Long. Speaking to reporters afterwards, they said Trump has endorsed their plan to add $8 billion over five years to help cover the cost for people with pre-existing illnesses who could otherwise be priced out of insurance markets.

Upton said it seemed likely the bill would pass the House, although Long said Republicans still seemed short of votes.

Long said he had opposed the legislation until the pre-existing conditions coverage was added. He said he had resisted Trump's arm-twisting, but that he now supported the bill. "The president said, 'Billy we really need you, man,'" Long said.

Conservatives who have stymied rollback efforts before said they support the moderates' latest plan, including the pre-existing conditions provision.

An initial rollback attempt failed in the House and was withdrawn by Republican leaders in March.