What started as a Twitter fight ended with one of the highest ranking Republicans in the U.S. Senate warning President Donald Trump may be on a course to incite a worldwide war.

Trump used his Sunday morning to blast U.S. Sen. Bob Corker on Twitter, lashing out at the Tennessee Republican days after Corker had his own harsh words for the administration.

Corker responded with his own rebuke on Twitter. But he left his most scathing comments for an interview with The New York Times, where he said Trump's threats aimed at other countries could set the U.S. “on the path to World War III.”

“I don’t think he appreciates that when the president of the United States speaks and says the things that he does, the impact that it has around the world, especially in the region that he’s addressing,” Corker said, according to a Times story published online Sunday evening.

"And so, yeah, it’s concerning to me.”

The back-and-forth started early Sunday in the form of three tweets from Trump. The president took credit for Corker deciding against running for re-election, saying he denied an endorsement after Corker "begged" for one.

"Senator Bob Corker 'begged" me to endorse him for re-election in Tennessee. I said 'NO' and he dropped out (said he could not win without...," the first tweet reads.

"..my endorsement). He also wanted to be Secretary of State, I said 'NO THANKS.' He is also largely responsible for the horrendous Iran Deal!," reads the second tweet.

Trump's third tweet says he expects Corker to be a negative voice, adding the former Chattanooga mayor didn't have the "guts to run."

Minutes later, Corker called the White House an "adult day care center."

"It's a shame the White House has become an adult day care center. Someone obviously missed their shift this morning," Corker tweeted.

More:Bob Corker stands up to the White House bully

Todd Womack, Corker's chief of staff, told the USA TODAY NETWORK the president’s Sunday morning accusations are false. Instead of Corker begging for the president’s endorsement, Womack said Trump called the senator early last week and asked him to reconsider his decision not to seek re-election.

During the call Trump said he would endorse Corker and help him campaign, Womack said.

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Corker, the chairman of the Senate Foreign Relations Committee, has been chastised by some conservative opponents for not doing more to block a procedural bill that allowed the Iran nuclear deal to proceed last year, although Corker opposed the deal.

Trump is facing an Oct. 15 deadline to re-certify that deal, in which the U.S. and five other world powers agreed to ease sanctions on Iran in exchange for international monitoring of Iran's nuclear program.

Last week, The Washington Post reported Trump planned to "decertify" the deal this week.

Sunday afternoon, Trump used a fourth tweet referencing Corker to again attack him for his role in the Iran nuclear deal.

"Bob Corker gave us the Iran Deal, & that's about it. We need HealthCare, we need Tax Cuts/Reform, we need people that can get the job done!" Trump tweeted.

During Trump's presidential campaign Corker was seen as a close adviser and ally. Corker has repeatedly said he was offered the vice presidency but declined.

After Trump's election, Corker has publicly critiqued the administration. He said the White House was in a "downward spiral" after reports emerged the president disclosed classified information to Russian officials. More recently, Corker questioned the president's competency to lead.

This week, in the wake of Secretary of State Rex Tillerson fending off reports he called the president a "moron," Corker said Tillerson and Defense Secretary James Mattis were "people that help separate our country from chaos."

"(Tillerson) from my perspective is an incredibly frustrating place where as I watch, and I can watch very closely on many occasions. l mean, he ends up not being supported in the way I would hope a secretary of state would be supported...I think he’s in a very trying situation, trying to solve many of the world’s problems a lot of times without the kind of support and help that I’d like to see him have."

More:Tennessee Democrats recalculate U.S. Senate race with Corker out

Corker doubled-down on those comments in his interview with The New York Times, also saying most of his Republican colleagues in the Senate share his concerns.

“Look, except for a few people, the vast majority of our caucus understands what we’re dealing with here,” Corker told the Times Sunday, adding that “of course they understand the volatility that we’re dealing with and the tremendous amount of work that it takes by people around him to keep him in the middle of the road.”

In late September, Corker announced he would not seek a third term. He had grappled with the decision for some time, he said, but he never mentioned the lack of a presidential endorsement as a reason he wouldn't run.

More:Sen. Bob Corker will not seek re-election next year

U.S. Rep. Marsha Blackburn announced she would seek the seat. The 15-year congressional veteran is an outspoken Trump supporter and is seen as a front-runner in the race.

Greg Korte and Michael Collins contributed to this article.

Reach Dave Boucher at 615-259-8892, dboucher@tennessean.com and on Twitter @Dave_Boucher1.