WASHINGTON — Sen. Bob Corker, the Republican chairman of the Foreign Relations Committee and an early supporter of Donald Trump’s candidacy, said Sunday that the White House had devolved into “an adult day care center” and warned that President Trump’s behavior is setting the nation “on the path to World War III.”

Corker’s comments, first made via Twitter and later in an interview with the New York Times, came in response to an extraordinary feud instigated by Trump in a Twitter tirade and marked the sharpest rebuke of this president by a senior Republican officeholder.

“He concerns me,” Corker told the Times. “He would have to concern anyone who cares about our nation.”

He added: “I know for a fact that every single day at the White House, it’s a situation of (senior administration officials) trying to contain him.”

The explosive comments not only breach what had been one of Trump’s few personal relationships on Capitol Hill, but also jeopardize the president’s legislative priorities. As chairman of the foreign relations panel, Corker, Tenn., will help determine the future of the Iran nuclear deal, and his support will be critical in passing broad tax cuts.

Trump alleged Sunday morning on Twitter that Corker recently “begged” him for his endorsement, did not receive it and decided to retire because he “didn’t have the guts” to run for reelection next year.

Corker tweeted a biting retort: “It’s a shame the White House has become an adult day care center. Someone obviously missed their shift this morning.”

Meanwhile, Corker’s chief of staff, Todd Womack, denied Trump’s characterization of his private conversations with the senator, who announced last month that he plans to retire and not seek reelection in 2018.

Trump’s outburst comes after Corker made headlines last week when he starkly suggested that the administration’s national security team provides the president with badly needed adult supervision.

Corker told reporters that Secretary of State Rex Tillerson, Defense Secretary Jim Mattis and White House Chief of Staff John Kelly “are those people that help separate our country from chaos.”

Trump, who has little tolerance for public criticism and prides himself on counterpunching those who cross him, took to Twitter on Sunday to attack Corker.

Trump tweeted: “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 … my endorsement). He also wanted to be Secretary of State, I said ‘NO THANKS.’ He is also largely responsible for the horrendous Iran Deal! Hence, I would fully expect Corker to be a negative voice and stand in the way of our great agenda. Didn’t have the guts to run!”

Womack said Trump has repeatedly offered to support Corker, and as recently as last week asked the senator to change his mind and run for reelection.

“The president called Senator Corker on Monday afternoon and asked him to reconsider his decision not to seek reelection and reaffirmed that he would have endorsed him, as he has said many times,” Womack said in a statement.

Apparently unwilling to let Corker’s “adult day care center” barb be the last word, Trump tweeted Sunday afternoon that Corker was an ineffective senator and could not “get the job done.”

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

The squabble comes just days before Trump is expected to “decertify” the Iranian nuclear pact reached with world powers in 2015 and punt to Congress a decision about whether to restore sanctions against Iran. This would be the first in a series of highly orchestrated steps that White House, State Department and congressional officials – primarily Corker, as chairman of the Foreign Relations Committee – have been planning for months.

Corker has been one of Tillerson’s few allies and staunch defenders in Washington, working closely on issues such as toughening sanctions on Russia and engaging North Korea diplomatically – two issues on which Trump has disagreed with Corker.

Corker also looks to play a key role in the upcoming debate over taxes.

One of the Senate’s most committed deficit hawks and outspoken members on budgetary issues, Corker already has expressed concerns with the Trump administration’s proposal on tax cuts, and his vote will be key to any deal getting done.

Trump’s attack also highlighted his increasingly strained relationship with Senate Republicans, who Trump feels have failed to deliver on his agenda.

In recent months, Trump has also gone after Senate Majority Leader Mitch McConnell, Ky., and Sens. Lindsey O. Graham, S.C., John McCain, Ariz., and Jeff Flake, Ariz., with cutting and sometimes personal insults.