Trump told the lawmakers that Republicans are "closer than people understand" on getting health care reform done and "have to pull through."
"We are in this room to deliver on our promise," Trump said. "We have no choice, we have to repeal and replace Obamacare. We can repeal it but the best is repeal and replace and let's get going. I intend to keep my promise and I know you will, too."
He added: "People are hurting. Inaction is not an option and frankly, I don't think we should leave town unless we have a health insurance plan, unless we can give our people great health care because we are close, we are very close."
Trump's call to repeal and immediately replace Obamacare puts him squarely at odds with Senate leadership, which -- after a series of stinging defeats -- has moved on to an effort to repeal the health care law and replace it later. Trump's position is also at odds with comments he made over the last 72 hours, when he publicly pushed to let Obamacare fail and to repeal it without a replacement plan.
White House spokeswoman Sarah Huckabee Sanders wouldn't say definitively whether Trump would follow his advice to senators and dispense with personal travel before health care reform is passed.
Speaking with reporters after the meeting, McConnell dodged a question about whether the White House and Senate leadership are out of sync, saying that Republicans now have "two options" before them.
"There is a large majority in our conference that want to demonstrate to the American people that they intend to keep the commitment they made in four straight elections to repeal Obamacare," he said. "I think we all agreed it is better to vote to repeal and replace. But we could have a vote on either and if we end up voting on repeal only, it will be fully amendable on the Senate floor and if it were to pass without any amendment at all, there is a two-year delay before it kicks in."
The top Republican added that while it is "pretty obvious we have had some difficulty in getting 50 votes to proceed," he intends to "vote on the motion to proceed next week."
He added: "So the takeaway from what I am telling you is no harm is done by getting on the bill."
Congress is set to depart Washington in mid-August, when members will return to their home states for the remainder of the month. Trump is also expected to spend a prolonged period away from the White House in August.
"I am ready to act," Trump said. "I have pen in hand, believe me, I am sitting in that office, I have pen in hand. You never had that before."
The meeting -- the second Trump luncheon with senators on the topic -- comes a day after Senate Majority Leader Mitch McConnell's backup plan to gut the Affordable Care Act was knocked off course by four senators who said they wouldn't go along with the bill. It marked the second-time McConnell hit a roadblock in less than 24 hours.
'He wants to remain a senator, doesn't he?'
Trump, seated between Sen. Tim Scott of South Carolina and Sen. Dean Heller of Nevada, joked about how he was among friends, even if some in the room bucked the party.
"They might not be very much longer, but that is OK," Trump said to laughs. "I think, I have to get them back."
After Heller said something inaudible to Trump, the two laughed and the President added, "You didn't go out there. This was the one we were worried about, you weren't there."
Heller was one of the first senators to stand against initial attempts to pass health care in the Senate. To the chagrin of Heller's colleagues, a super PAC tied to Trump ran ads against the vulnerable Nevada senator who is up for reelection in 2018.
After the friendly exchange, Trump said, "Look, he wants to remain a senator, doesn't he?"
Heller looked visibly surprised by the comment.
Trump's argument to the lawmakers boiled down to Republicans have to keep their word to the American people and pass a health care bill.
"Any senator who votes against starting debate," Trump said, sitting with several senators against doing just that, "is really telling America that you are fine with Obamacare."
The lawmakers who stood against Trump and McConnell on health care all attended the Wednesday meeting -- including Sens. Mike Lee and Jerry Moran, who blocked the second attempt to pass the bill, and Sens. Susan Collins, Rob Portman, Shelley Moore Capito and Lisa Murkowski, who blocked the most recent clean repeal attempt.
Three Republican senators who support repealing Obamacare -- Johnny Isakson, Richard Burr and John McCain -- did not attend the Wednesday meeting. McCain is still in Arizona recovering from surgery to remove a blood clot.
Marc Short, the White House director of legislative affairs, told reporters on Wednesday that Trump and the senators recognized health care is "not something we can walk away from" and that the President plans to take a more active role in selling the bill.
"I think you'll see that in one form or the other," Short said. "I think several senators raised the notion that the President could be extremely helpful to them in making that case and I think that he was receptive to that."
To follow up on the meeting, Short said that White House officials will meet with skeptical senators on Capitol Hill on Wednesday night.
Despite the two lunches he has hosted and his frequent tweets on the topic, Trump has left the detailed negotiating to Vice President Mike Pence.
The President has worked the phones, and continued to do so on Tuesday with a call to Sen. Mike Lee, a Utah Republican.
According to a Lee aide said, Trump was lobbying the senator to support going back to repeal and immediately replace, a strategy McConnell had already abandoned. The gist of the call was "how to get a good repeal bill passed," the aide said, but the discussion centered around how to get the bill that McConnell dispatched earlier this week -- the Better Care Reconciliation Act -- passed.
During the call, the aide said, Lee reiterated to Trump his request for the consumer freedom amendment. A White House official declined to detail who else Trump called on Tuesday.
Trump's activism on the bill has come primarily over the phone. The President made calls to skeptical senators earlier this month during a trip to Paris and spoke with lawmakers over the weekend as he took in a golf tournament at his private club in New Jersey.
But Wednesday, in the wake of McConnell's failed efforts, he tried to lobby lawmakers in person.
"I will be having lunch at the White House today with Republican Senators concerning healthcare," Trump tweeted on Wednesday morning. "They MUST keep their promise to America!"
Trump said Tuesday he was "very disappointed" that the Senate was unable pass their initial plan, but pledged he, his White House and Senate Republicans will not take the blame for Obamacare's failures.
"I think we're probably in that position where we'll just let Obamacare fail. We're not going to own it," Trump said. "I'm not going to own it, I can tell you. The Republicans are not going to own it. We'll let Obamacare fail."
CNN's Lauren Fox contributed to this report.