WASHINGTON (AP) — President Joe Biden on Sunday urged Americans to reject political violence and recommit themselves to resolving their differences peacefully, saying the upcoming presidential election will be a "time of testing" in the aftermath of the attempted assassination of former President Donald Trump.

In a prime-time national address from the Oval Office, Biden said political passions can run high but "we must never descend into violence." The president said his party and the Republicans can compete forcefully over different policy visions — but must do it in a civil fashion.

"All of us now face a time of testing as the election approaches," Biden said. "There is no place in America for this kind of violence — for any violence. Ever. Period. No exception. We can't allow this violence to be normalized."

Biden spoke for six minutes in his third address to the nation since Saturday evening's attack by a shooter that left Trump with a bloodied ear, killed one rallygoer and seriously injured two others. His warning came hours after FBI Deputy Director Paul Abbate said agents have seen increasingly violent rhetoric online since the attack at the Trump rally.

Since the shooting, the president and his team had been grappling with how to calibrate the political path forward after the weekend attack targeting the very person Biden is trying to defeat in November's election. Biden sharply condemned the attack, but indicated he plans to continue to press his campaign agenda and has "no doubt" Republicans will do the same when they open the Republican National Convention in Milwaukee on Monday.

He emphasized that said those disagreements must remain peaceful.

"We can do this," Biden pleaded, saying the nation was founded on a democracy that gave reason and balance a chance to prevail over brute force. Biden also warned that political tensions were being inflamed by a balkanized media environment and exploited by American enemies.

"Here in America we need to get out of our silos, where we only listen to those with whom we agree, where misinformation is rampant, where foreign actors fan the flames of our division to shape the outcomes consistent with their interests, not ours," Biden said.

Earlier Sunday, Biden was briefed in the White House Situation Room and condemned the attempted assassination of Trump as "contrary to everything we stand for as a nation." He said he was ordering an independent security review of how such an attack could have happened.

The president said he has also directed the U.S. Secret Service to review all security measures for the RNC. Hours later, Audrey Gibson-Cicchino, the Secret Service's coordinator for the convention, said the weekend attack against Trump did not warrant any changes to the agency's security plan for the event and officials "are fully prepared."

Biden promised a "thorough and swift" review and asked the public not to "make assumptions" about the shooter's motives or affiliations.

The president said he and first lady Jill Biden were praying for the family of Corey Comperatore, a former fire chief who was shot and killed during the Trump rally Saturday night in Butler, Pennsylvania.

"He was protecting his family from the bullets," Biden said. "God love him."

The president also said he'd had a "short but good conversation" with Trump in the hours after the shootings and said he was "sincerely grateful" that the former president is "doing well and recovering."

Trump, who has called for national resilience since the shooting, posted on his social media account after Biden's remarks, "UNITE AMERICA!"

Biden, who has set out to brand Trump as a dire threat to democracy and the nation's very founding principles, put a temporary pause on such political messaging after the shooting. Shortly after Saturday night's attack, Biden's reelection campaign froze "all outbound communications" and worked to pull down its television ads.

The president also postponed a planned trip to Texas on Monday, where he was to speak on the 60th anniversary of the Civil Rights Act at the Lyndon B. Johnson presidential library. An NBC News interview between Biden and anchor Lester Holt will now occur at the White House, instead of in Texas, as initially planned.

Biden's campaign said that, after the NBC interview airs on Monday night, the Democratic National Committee "will continue drawing the contrast" with Trump over the course of the GOP convention. It was unclear when campaign ads will resume.

Biden still plans to make a planned trip to Las Vegas, which will include a campaign event Wednesday. Vice President Kamala Harris postponed her planned campaign trip to Florida on Tuesday, where she had been set to meet with Republican women.

Trump, meanwhile, arrived Sunday evening in Milwaukee for the Republican convention, where criticism of Biden and the Democrats is sure to be searing.

The weekend developments were only the latest upheaval in a campaign that has been extraordinarily topsy-turvy in recent weeks.

Biden's shaky debate performance on June 27 so spooked his own party that some top surrogates and donors turned on him, and nearly 20 Democratic members of Congress called on the president to leave the race outright. Facing mounting questions about whether he was fit for a second term, Biden and his top advisers have been scrambling to salvage his campaign by adding events around the country and more aggressively criticizing Trump.

Saturday's attack upended — at least temporarily — that counteroffensive. The campaign hoped that Sunday's Oval Office address let Biden further drive home his point about unity while demonstrating leadership that could assuage nervous critics within his own party.

"We'll debate and we'll disagree, that's not going to change," Biden said in his afternoon remarks. "But we'll not lose sight of who we are as Americans."

Biden tied Saturday's shooting to other incidents of political violence, from the 2017 death of a counterprotester at a white supremacist rally in Charlottesville, Virginia, to the Capitol insurrection on Jan. 6, 2021, by Trump supports seeking to prevent the certification of the Electoral College count.

Although investigators are still in the early stages of determining what occurred and why, some Biden critics were calling out the president for telling donors in a private call Monday that "it's time to put Trump in the bullseye."

A person familiar with those remarks said 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. 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."