President Donald Trump continued to put pressure on Republican senators Wednesday morning as the chamber debates possible plans to repeal Obamacare.

In a tweet, Trump targeted Sen. Lisa Murkowski, R-Alaska, for her Tuesday vote opposing a procedural motion to start debate on one of multiple potential plans to overhaul the American health-care system. Trump contended that she "let the Republicans, and our country, down yesterday."

Trump: Senator @lisamurkowski of the Great State of Alaska really let the Republicans, and our country, down yesterday. Too bad!

Murkowski and Sen. Susan Collins, R-Maine, have both pushed for a bipartisan fix for Obamacare's flaws and were the only GOP senators who voted against starting a debate on Tuesday. In a statement after the vote, Murkowski said she did so to encourage the Senate to go through the normal committee process, adding that she wants to "find solutions that benefit all Americans by increasing access and reducing the cost of care."

In comments to NBC News on Wednesday, Murkowski responded by saying that she cast her vote while trying to "do the best by Alaska." Murkowski, who was re-elected to a six-year term last year, also shrugged off any concerns about Trump's tweet being an electoral threat.

Trump's jab at Murkowski follows veiled threats to senators on Tuesday night.

"Any senator who votes against repeal and replace is telling America that they are fine with the Obamacare nightmare," Trump said at a rally in Youngstown, Ohio. "And I predict they'll have a lot of problems."

Trump did not specify what those "problems" would be. He has previously made a joking reference to at least one senator, Republican Dean Heller of Nevada, losing his seat if he does not support Obamacare replacement efforts.

The Senate on Tuesday voted by the narrowest margin to start debate on the House-passed Obamacare replacement plan and move toward passing its own version of repeal. That is, 50 of 52 Republican senators supported the procedural motion, and Vice President Mike Pence had to cast a tie-breaking vote.

The vote came after weeks of setbacks for Republicans as party divisions stalled multiple versions of their plans to overhaul the American health-care system.

Passing the motion to proceed does not mean Republicans have a consensus on a bill they can pass. The procedural measure starts a complicated period in which senators are expected to float and vote on varying alternatives for reshaping Obamacare. That process started Tuesday night.

Reaching an agreement on a plan to simply repeal parts of the landmark health-care law or replace it still appears difficult.

Senate Majority Leader Mitch McConnell said Tuesday that he hopes to have a measure that can pass the Senate and advance to the House or a conference between the House and Senate by the "end of the week."