The announcement of Biden's planned remarks came after homeland security and law enforcement officials briefed Biden, and the White House continued to call for national unity and condemn the stunning act of violence.

Vice President Kamala Harris joined Biden for an update from top investigators, including Attorney General Merrick Garland, Department of Homeland Security Secretary Alejandro Mayorkas and FBI Director Christopher Wray. Also participating were White House National Security Adviser Jake Sullivan and Kim Cheatle, director of the U.S. Secret Service.

Biden quickly denounced the shooting and talked to Trump on Saturday night. His campaign team, meanwhile, is grappling with how to manage the political implications of an attack on the man who Biden hopes to defeat in the November election.

Trump himself called for unity and national resilience, and aides said he was in "great spirts and doing well" after being injured during a rally in Butler, Pennsylvania. He is pushing ahead with plans to attend this week's Republican National Convention in Milwaukee, where criticism of Biden and the Democrats is sure to be searing.

In the moments after the shooting, Biden's reelection campaign said it was putting a hold on "all outbound communications and working to pull down our television ads as quickly as possible." It was not clear how long the suspension would last.

Harris postponed a planned campaign trip to Florida on Tuesday, where she was to meet with Republican women voters in light of Saturday's shooting, according to a campaign official.

Investigators are still in the early stages of determining what occurred and why. But some Biden critics are calling out the president for telling donors on a private call July 8 that "it's time to put Trump in the bullseye."

A person familiar with those remarks said Sunday that the president was trying to make the point that Trump had gotten away with a light public schedule after last month's debate while the president himself faced intense scrutiny from many even within his own party for his dismal performance in the faceoff.

The person spoke on the condition of anonymity to more freely discuss private conversations.

In the donor call, Biden said: "I have one job and that's to beat Donald Trump ... I'm absolutely certain I'm the best person to be able to do that."

He continued: "So, we're done talking about the debate. It's time to put Trump in the bullseye. He's gotten away with doing nothing for the last 10 days except ride around in his golf cart, bragging about scores he didn't score ... Anyway I won't get into his golf game."

In his initial response to the shooting on Saturday night, Biden condemned the attempt on Trump's life. The White House also said then that the two men spoke, but did not release details.

"Look, there's no place in America for this kind of violence," Biden said Saturday night, before hustling back to the White House from Rehoboth Beach, Delaware, where he had been spending the weekend. "It's sick. It's sick. It's one of the reasons why we have to unite this country. We cannot allow for this to be happening. We cannot be like this. We cannot condone this."