(CNN) - Joe Biden pledged to undo President Donald Trump's foreign policy moves in a speech in which the former vice president laid out how he would seek to restore pre-Trump international norms and "place America back at the head of the table."
The address, in New York City on Thursday, came as Biden attempts to shift the focus of his bid for the 2020 Democratic presidential nomination away from fights with his intra-party rivals and to how he would challenge Trump in a general election.
The former vice president warned that democracies are under the most "intense pressure" faced since the 1930s. He called Trump "insincere, ill-informed and impulsive, and sometimes corrupt."
"Donald Trump's brand of America first has too often led to America alone, making it much harder to mobilize others to address the threats to our common well-being," Biden said.
He added: "If we give Donald Trump four more years, we'll have a great deal of difficulty being able to recover America's standing in the world and our capacity to bring nations together."
Biden also sought to emphasize his experience to Democratic primary voters by arguing there would be a limited window to reverse Trump's influence. "We only have one opportunity to reset this democracy after Trump -- we have to prepare to make the most of it," he said.
In the Democratic primary fight, Biden's long foreign-policy record has come under renewed scrutiny by some of his rivals, particularly his 2002 vote to authorize the Iraq War. Sen. Bernie Sanders of Vermont and others have sharply criticized that decision and its aftermath.
Washington Gov. Jay Inslee, another 2020 Democratic rival, said Thursday before Biden's speech said that it was "a horrendous lack of judgment to give George Bush the authority to go to war."
"I do believe he has to take responsibility for that. Part of that is to apologize for that vote. I think that that would be appropriate. And I would like to know how he made such a misjudgment. ... I think the vice president owes an explanation to the American people about why he made that horrendous mistake," Inslee said.
Biden on Thursday did not directly address his Iraq vote -- which he apologized for in 2005 -- but did acknowledge mistakes in US foreign policy.
"American leadership is not infallible. We've made missteps and mistakes," he said. "Too often we have relied solely on the might of our military instead of drawing on the full array of our strengths."
He said he would reinstate daily press briefings at the White House, the State Department and the Pentagon. He also said it is "time to end forever wars."
In the speech, Biden said he would return to international agreements negotiated under former President Barack Obama -- including the Iran nuclear deal "if Tehran returns to compliance with the deal" and the Paris climate accord.
"If we don't get climate change right, nothing else matters much," he said.
Biden did not mention trade deals that were negotiated by Obama's administration but faltered when Trump took office, such as the Trans-Pacific Partnership, which was designed to counter China's growing economic influence among Pacific Rim countries. He called for "new rules" on trade that would emphasize labor and environmental protections.
The centerpiece of his effort to return to international cooperation: a summit that Biden said he would call among the world's democracies, non-governmental organizations and corporations -- particularly tech and social media companies -- to seek a common agenda to protect their shared values.
Such a summit would push companies like Facebook, Google and Twitter -- where Russian trolls reached American voters during the 2016 election -- to combat challenges such as surveillance, censorship and the spread of hate speech.
"America's openness fueled their success," Biden said. "Now they have a duty to make sure their algorithm and platform are not misused to sow division here at home, to empower the surveillance state, to facilitate oppression and censorship in China or elsewhere, to spread hate or to spur people to violence."
Biden's proposal for a summit comes the same day Trump hosts some of the right-wing media universe's biggest stars -- but not officials from Facebook and Twitter, who were not invited -- at what's being billed as a "social media summit" at the White House.
The foreign policy address is the latest effort by Biden to reset his campaign -- following a shaky debate performance late last month -- in hopes of persuading voters that he is the strongest candidate to defeat Trump.
The speech is part of the campaign's attempt to showcase what it perceives as key strengths of Biden, who traveled the globe as chairman of the Senate Foreign Relations Committee and as vice president. Rather than new policy, his remarks are intended to signal a return to a pre-Trump era.
Biden said he would "place America back at the head of the table."
"The world does not organize itself, and if we do not shape the norms and institutions that govern relations among nations, rest assured that some nation will step into the vacuum -- or no one will, and chaos will prevail," he said.