Utah Senator Mitt Romney said Friday that he's not sure if he'll endorse President Trump for a second term and that he may not throw his weight behind anyone during the 2020 campaign.

‘I don't think endorsements are worth a thimble of spit,’ the Republican former presidential candidate told reporters during an annual gathering of political leaders and wealthy donors in the Utah ski-resort town of Park City.

‘I wouldn't be surprised if I stay out of the endorsements.’

Romney wrote in the name of his wife, Ann, on his 2016 ballot, and said, 'I still think she's doing a fine job.'

Senator Mitt Romney of Utah (above) says he may not endorse President Trump for re-election next year

During the 2016 election, Romney gave a highly critical speech of Trump, calling him a 'a phony, a fraud.'

Trump, in return, mocked Romney for losing the 2012 presidential election.

After Trump won the presidency, he considered Romney for the position of secretary of state, but ultimately chose former Exxon CEO Rex Tillerson.

The senator on Saturday said it's still too early for endorsements but repeated his view that Trump will likely win re-election in 2020 as an incumbent presiding over a strong economy, though ‘it's not a sure thing.’

Romney has been one of the president's fiercest GOP critics at times, though he's also supported Trump on other issues.

The president endorsed Romney's Senate run.

Romney said he opposed Trump's proposal to impose tariffs on Mexico to force the U.S. ally to stem the flow of migrants.

Trump had set a Monday deadline to impose the tariffs but the U.S and Mexico reached a deal Friday avert them.

Many Republicans and businesses had urged Mr. Trump to reconsider the plan, which could have enormous economic implications for both countries.

Romney agreed, saying Mexico is a friend to the U.S.

‘Punishing Mexico in some way is, in my opinion, a very bad idea. It's also expensive for Americans,’ Romney said.

Romney has emerged as a leading anti-Trump voice within the Republican Party

The former Massachusetts governor does support the use of tariffs on China, saying it has been abusing global free-trade rules.

‘President Trump was right to push back hard on China, and I support that effort,’ he said.

But he added he would have gathered a coalition of allies to present a united front to the world's most populous nation.

Romney warned against underestimating China, saying it's an increasingly innovative on technologies like artificial intelligence.

In April, Romney said he was 'sickened' and 'appalled' by what the Mueller Report revealed about the Commander-in-Chief's conduct

‘I don't think there's much recognition in the United States about the long-term issues with China,’ he said during a speech at the E2 Summit, founded six years ago and now chaired by former U.S. House Speaker Paul Ryan.

‘We haven't laid out a real comprehensive strategy to say, “How do we up our game dramatically?”’

In April, Romney said he was 'sickened' and 'appalled' by what the Mueller report revealed about the Commander-in-chief's conduct.

Special Counsel Robert Mueller concluded a two-year investigation into alleged Russian meddling in the 2016 elections.

While Mueller said there was insufficient evidence that Trump or anyone associated with his campaign conspired with Russia, the report left open the possibility that the president tried to impede the investigation.

Earlier this year, Romney had some strong words for Trump in a blistering op-ed where he said 'the president has not risen to the mantle of the office'.

Earlier this year, Romney wrote an op-ed in The Washington Post blasting Trump

After Trump won the election, he considered Romney for the secretary of state position. But the president-elect eventually decided on former Exxon CEO Rex Tillerson. Romney and Trump are seen above at Trump International Golf Club, November 19, 2016 in New Jersey

The 72-year-old Republican, who was the GOP presidential nominee in 2012, revealed he's highly critical of Trump's two years in office.

'It is well known that Donald Trump was not my choice for the Republican presidential nomination. After he became the nominee, I hoped his campaign would refrain from resentment and name-calling. It did not,' he wrote in an op-ed piece for the Washington Post published on January 1.

'When he won the election, I hoped he would rise to the occasion. His early appointments of Rex Tillerson, Jeff Sessions, Nikki Haley, Gary Cohn, H.R. McMaster, Kelly and Mattis were encouraging. But, on balance, his conduct over the past two years, particularly his actions this month, is evidence that the president has not risen to the mantle of the office,' Romney added.

He said that Trump's job in the White House and as the nation's leader is to 'demonstrate the essential qualities of honesty and integrity', something he has failed to do.

'With the nation so divided, resentful and angry, presidential leadership in qualities of character is indispensable. And it is in this province where the incumbent's shortfall has been most glaring,' Romney wrote.