"His pitch is he needs me," Hatch said of Trump, according to CNN. "Things are going to be just fine."
Hatch's comments came a day after Trump picked former Utah Gov. Jon Huntsman to serve as the U.S. ambassador to Russia, and two days after Hatch and Huntsman huddled in the U.S. Capitol.
Huntsman had been seen as a possible challenger to Hatch in 2018, and a Salt Lake Tribune-Hinckley Institute of Politics poll of Utah voters in January showed Huntsman would easily best the senator, 62 percent to 21 percent. Even among Republicans, Huntsman beat Hatch 49 percent to 35 percent.
That same survey showed 78 percent of voters opposed Hatch seeking re-election.
Hatch told CNN that Huntsman was a "longtime friend" and didn't believe he would have mounted a campaign against him.
"I don't think he would have ever run against me," Hatch said. "He didn't really want to run for Senate."
Hatch's office said later Thursday that the senator wasn't firm in his decision to run again.
"Senator Hatch appreciates the encouragement he's receiving to run for re-election," Hatch's office said in a statement. "While he has not made a final decision about his plans for 2018, he has made plans thus far to ensure all options remain on the table."
Gov. Gary Herbert praised Hatch and said he wasn't surprised.
"Senator Hatch has been a very great ally for the state of Utah," Herbert said. "He's certainly been there and served with distinction for 40 years and will still do another two years."
It's his decision, Herbert added.
"I don't think it's too surprising because we've seen some signs of this over the last number of months of him talking about he may change his mind from saying he won't run again."
Hatch's comments irked some Utahns who say the senator is going back on his promise.
Connor Boyack, president of the Libertas Institute, called Hatch a "liar" on Twitter.