WASHINGTON — In a high-profile televised address, U.S. President Joe Biden ripped his likely Republican challenger Donald Trump for “bowing down” to Russian President Vladimir Putin and urged Congress to pass aid for Ukraine, warning that democracy around the world was under threat.

In the annual State of the Union address, Biden came out swinging from the get-go against Putin and Trump — whom he called “my predecessor” without mentioning him by name — and on behalf of Ukraine, as he sought to win over undecided voters ahead of November’s election.

The March 7 address to a joint session of Congress this year carried greater significance for the 81-year-old Biden as he faces a tough reelection in November, mostly likely against Trump. The president, who is dogged by questions about his physical and mental fitness for the job, showed a more feisty side during his hourlong speech, drawing a sharp contrast between himself and Trump on a host of key foreign and domestic issues.

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Biden denounced Trump for recent remarks about NATO, the U.S.-led defense alliance that will mark its 75th anniversary this year, and compared him unfavorably to former Republican President Ronald Reagan.

“Bowing down to a Russian leader, it is outrageous, dangerous, and unacceptable,” Biden said, referring to Trump, as he recalled how Reagan — who is fondly remembered by older Republicans — stood up to the Kremlin during the Cold War.

At a campaign rally last month, Trump said that while serving in office he warned a NATO ally he “would encourage” Russia “to do whatever the hell they want” to alliance members who are “delinquent” in meeting defense-spending goals.

The remark raised fears that Trump could try to pull the United States out of NATO should he win the election in November.

Biden described NATO as “stronger than ever” as he recognized Swedish Prime Minister Ulf Kristersson in the audience. Earlier in the day, Sweden officially became the 32nd member of NATO, ending 200 years of nonalignment. Sweden applied to join the defense alliance after Russia’s full-scale invasion of Ukraine in 2022. Finland became a NATO member last year.

Biden called on Congress to pass a Ukraine aid bill to help the country fend off a two-year-old Russian invasion. He warned that should Russia win, Putin will not stop at Ukraine’s border with NATO.

A group of right-wing Republicans in the House of Representatives have for months been holding up a bill that would allocate some $60 billion in critical military, economic, and humanitarian aid to Ukraine as it defends its territory from Russian invaders.

The gridlock in Washington has starved Ukrainian forces of U.S. ammunition and weapons, allowing Russia to regain the initiative in the war. Russia last month seized the eastern city of Avdiyivka, its first victory in more than a year.

“Ukraine can stop Putin if we stand with Ukraine and provide the weapons it needs to defend itself,” Biden said.

“My message to President Putin…is simple. We will not walk away. We will not bow down. I will not bow down,” Biden said.

Trump, who has expressed admiration for Putin, has questioned U.S. aid to Ukraine, though he recently supported the idea of loans to the country.

Biden also criticized Trump for the former president’s attempt to overturn the results of the 2020 election, saying those efforts had posed a grave threat to democracy at home.

“You can’t love your country only when you win,” he said, referring not just to Trump but Republicans in Congress who back the former president’s claim that the 2020 election was rigged.

Biden “really strove to distinguish his policies from those of Donald Trump,” said Kathryn Stoner, a political-science professor at Stanford University and director of its Center on Democracy, Development, and the Rule of Law.

By referencing Reagan, Biden was seeking “to appeal to moderate Republicans and independents to remind them that this is what your party was — standing up to Russia,” she told RFE/RL.

The State of the Union address may be the biggest opportunity Biden has to reach American voters before the election. More than 27 million people watched Biden’s speech last year, equivalent to about 17 percent of eligible voters.

Biden’s address this year carries greater importance as he faces reelection in November, most likely against Trump. The speech may be the biggest opportunity he has to reach American voters before the election.

Trump won 14 of 15 primary races on March 5, all but wrapping up the Republican nomination for president. Biden beat Trump in 2020 but faces a tough reelection bid amid low ratings.

A Pew Research poll published in January showed that just 33 percent of Americans approve of Biden’s job performance, while 65 percent disapprove. Biden’s job-approval rating has remained below 40 percent over the past two years as Americans feel the pinch of high inflation and interest rates.

Biden, the oldest U.S. president in history, has been dogged by worries over his age. Two thirds of voters say he is too old to effectively serve another term, according to a recent Quinnipiac poll.

Last month, a special counsel report raised questions about his memory, intensifying concerns over his mental capacity to run the country for four more years.

As a result, Biden’s physical performance during the address was under close watch. Biden was animated during the speech and avoided any major gaffes.

“I thought he sounded really strong, very determined and very clear,” Stoner said.

Instead of avoiding the subject of his age, Biden took it head on, saying the issue facing our nation “isn’t how old we are, it’s how old our ideas are.”

He warned Trump was trying to take the country back to a darker period.

“Some other people my age see a different story: an American story of resentment, revenge, and retribution,” Biden said, referring to the 77-year-old Trump.