"They all have given me a commitment that they're voting for our health plan."
The bill, which Trump said he backs "100 percent," faces a crunch vote next week in the House of Representatives.
Several Republicans have expressed deep reservations, putting the outcome of the vote in doubt.
Some conservatives have said the Republican plan is too similar to Obamacare in that it replaces that law's health coverage subsidies with refundable tax credits that fulfill a similar role.
They also call for changes to the provision that rolls back the expansion of Medicaid, the health coverage program for the poor and the disabled.
Republican Study Committee chairman Mark Walker, who attended Friday's meeting with Trump, has said his group's 170 members support instituting work requirements for able-bodied, childless adults on Medicaid.
Some conservatives also want to see the Medicaid expansion ended after 2017, not 2020 as required in the bill.
Some moderate Republicans are nervous that the plan would cause struggling families to suffer, a prospect highlighted this week by a damning congressional projection that 24 million people could lose insurance within a decade under the new bill.
It was unclear what transpired in the White House meeting to bring concerned conservatives on board, but Trump signaled that they discussed alterations to the legislation.
"We have rejiggered it," Trump told reporters afterward. "We've done some great things," and "health care looks like it's really happening."
The key question is whether Trump is able to convince enough Republicans to toe the line and help pass the bill in the House, where Republicans can afford no more than 21 defections if all Democrats vote no, as expected.
House Republican Justin Amash was having none of Trump's strongarm tactics.
"Absolutely not true that conservatives have flipped to yes on the health care bill," Amash wrote on Twitter. "It doesn't repeal Obamacare. It remains a disaster."