WASHINGTON — White House officials again lowered the American flag atop the building to half-staff Monday afternoon after intense criticism of the administration’s response to Senator John McCain’s death and bipartisan calls from Congress to lower the flag.

‘‘Despite our differences on policy and politics, I respect Senator John McCain’s service to our country and, in his honor, have signed a proclamation to fly the flag of the United States at half-staff until the day of his interment,’’ President Trump wrote late in the day, breaking his two-day silence on the Republican senator from Arizona.

The two had a tumultuous relationship and McCain was occasionally the subject of the president’s barbs.

The president also said he had requested that Vice President Mike Pence speak at Capitol Hill services honoring McCain on Friday, and chief of staff John Kelly, Defense Secretary Jim Mattis, and Ambassador John Bolton to represent his administration at the funeral. And he said he had authorized military assistance for the funeral and burial.

The move came after White House officials had raised the flag earlier in the day, and Trump ignored almost a dozen shouted questions about McCain while White House staffers convulsed over his reaction.

Trump had blocked efforts to release a statement honoring McCain and calling him a ‘‘hero,’’ instead expressing condolences to McCain’s family via Twitter on Saturday night.

US code calls for flags to be lowered in the event of the death of a member of Congress ‘‘on the day of death and the following day.’’ But presidents have the power to issue proclamations extending that period and have done so routinely.

The American Legion, a veterans organization, had called on Trump to treat McCain with more reverence.

‘‘On behalf of The American Legion’s two million wartime veterans, I strongly urge you to make an appropriate presidential proclamation noting Senator McCain’s death and legacy of service to our nation and that our nation’s flag be half-staffed through his internment,’’ said Denise Rohan, the group’s national commander.

In a tweet Monday morning, a spokesman for Senate minority leader Charles Schumer, Democrat of New York, said that he and Senate majority leader Mitch McConnell had asked the Department of Defense to ‘‘provide necessary support so that US flags on all government buildings remain at half mast through sunset on the day of Senator McCain’s interment.’’

After facing a day of criticism, the president released his statement. He also said he had requested that Vice President Mike Pence speak at Capitol Hill services honoring McCain on Friday, and chief of staff John Kelly, Defense Secretary Jim Mattis and Ambassador John Bolton to represent his administration at the funeral. And he said he had authorized military assistance for the funeral and burial.

Trump was not invited to the funeral. Former presidents Barack Obama and George W. Bush are scheduled to deliver eulogies.

In a final letter released Monday, McCain expressed his deep gratitude and love of country and implored Americans to put aside ‘‘tribal rivalries’’ and focus on what unites them.

Rick Davis, former presidential campaign manager for McCain who is serving as a family spokesman, read the farewell message Monday at a press briefing in Phoenix.

In the statement, McCain reflected on the privilege of serving his country and said he tried to do so honorably. He also touched on today’s politics.

‘‘Do not despair of our present difficulties but believe always in the promise and greatness of America, because nothing is inevitable here,’’ McCain wrote. ‘‘Americans never quit. We never surrender. We never hide from history. We make history.’’

McCain died Saturday from an aggressive form of brain cancer.

Extensive plans to honor the senator were taking shape. McCain will lie in state Wednesday in the Arizona State Capitol on what would have been his 82nd birthday. A funeral will be conducted Thursday at North Phoenix Baptist Church with former vice president Joe Biden speaking.

In Washington, McCain will lie in state Friday in the Capitol Rotunda with a formal ceremony and time for the public to pay respects. On Saturday, a procession will pass the Vietnam Veterans Memorial and arrive for a funeral at Washington National Cathedral. Former presidents George W. Bush and Barack Obama are expected to speak at the service.

McCain, a former Navy pilot, is scheduled to be buried Sunday at the Naval Academy in Annapolis, Md.

McConnell paid tribute to his colleague on Monday by recalling their legislative battles while echoing the late senator’s belief that there’s more that unites than divides Americans.

Speaking from the Senate floor, McConnell said that although McCain served the state of Arizona in Congress, ‘‘he was America’s hero all along.’’

He spoke near McCain’s desk in the Senate, which has been draped in black and adorned with white roses in his honor.

The White House flag episode was the latest involving Trump and the powerful American symbol. For months, he has castigated NFL players who choose to kneel during the national anthem, accusing them at political rallies and in other settings of disrespecting the flag.

Trump has also threatened to strip the citizenship of those who burn the flag.

Senate leaders had sought to have flags remain at half-staff until the burial service for McCain on Sunday.

On Monday morning, flags at the US Capitol, where McCain served two terms in the House and six terms in the Senate, remained at half-staff. Congressional aides said they expect that the tribute there will continue.

At federal buildings around Washington, some flags continued to fly at half-staff while a growing number were raised as the day continued.

In 2009, after the death of Senator Edward M. Kennedy, Democrat of Massachusetts, Obama ordered flags to fly at half-staff for five days.

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Trump’s proclamation on McCain, as provided by the White House:

“Despite our differences on policy and politics, I respect Senator John McCain’s service to our country and, in his honor, have signed a proclamation to fly the flag of the United States at half-staff until the day of his interment.

“I have asked Vice President Mike Pence to offer an address at the ceremony honoring Senator McCain at the United States Capitol this Friday.

“At the request of the McCain family, I have also authorized military transportation of Senator McCain’s remains from Arizona to Washington, D.C., military pallbearers and band support, and a horse and caisson transport during the service at the United States Naval Academy.

“Finally, I have asked General John Kelly, Secretary James Mattis, and Ambassador John Bolton to represent my Administration at his services.”