President Donald Trump is ramping up his outreach to Senate Republicans as their Obamacare repeal effort hangs in the balance, dialing up an undecided conservative senator over the weekend and inviting several other key GOP senators to the White House for a private meeting Monday night.

White House press secretary Sean Spicer said Monday that Trump plans to host some Republicans to discuss the repeal push. Spicer didn’t disclose the invite list, but Sen. Lamar Alexander of Tennessee and James Lankford of Oklahoma are among the senators who will attend, according to Republican aides.

“There’s been a very robust discussion with House and Senate leadership,” Spicer said Monday. “We’re going to do what we did last time.”

Trump also spoke privately via phone with Sen. Mike Lee on Saturday, according to a spokesman for the conservative Utah senator. Lee is pressing to include a full version of legislation he authored that would allow insurers to sell cheaper health coverage that doesn’t comply with key Obamacare regulations, as long as the companies offer plans that do.

The senator told Trump that he was still undecided on the latest version of the GOP repeal measure. Two GOP senators — Sens. Rand Paul of Kentucky and Susan Collins of Maine — have said they won’t vote to begin debate on the bill.

Sen. Orrin Hatch (R-Utah), the chairman of the Finance Committee, was at the White House earlier Monday to meet with administration staff on health care and other topics, he said.

"I think we have the chance to make it more palatable,” Hatch said Monday. “I don’t see how it hurts anything except it shortens the so-called August recess."

Matthew Nussbaum and Jennifer Haberkorn contributed to this report.