WASHINGTON, Feb 19 (Reuters) — U.S. President Joe Biden on Friday drew a sharp contrast with the foreign policy of his much-derided predecessor, Donald Trump, vowing to end transactional diplomacy and promote democracy over autocracies.

The Democratic president, sworn in a month ago, used his first big appearance on the global stage - a "virtual visit" to Europe - to try to re-establish the United States as a multilateral team player after four years of divisive "America First" policies pursued by Trump.

In an online speech to the Munich Security Conference, Biden drew a stark difference with the more transactional foreign policy practiced by Trump, who angered allies by breaking off global accords and threatening to end defense assistance unless they toed his line.

"Our partnerships have endured and grown through the years because they are rooted in the richness of our shared democratic values. They’re not transactional. They’re not extractive. They’re built on a vision of the future where every voice matters," he said.

"I know, I know the past few years of strain (have) tested our transatlantic relationship, but the United States is determined - determined to re-engage with Europe," he said.

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Watch a video of Biden's speech below.

Biden told U.S. allies that they must stand firm against the challenges posed by China, Russia and Iran, saying Russia was seeking to weaken the transatlantic alliance and calling for a united front to counter what he called China's abusive economic practices.

Biden arrived bearing gifts - a $4 billion pledge of support for global coronavirus vaccination efforts, the re-entry of the United States into the Paris climate accord and the prospect of a nearly $2 trillion spending measure that could bolster both the U.S. and global economies.

Biden first met G7 leaders from Britain, France, Germany, Italy, Canada and Japan by videoconference on Friday. He plans to join them for an in-person summit hosted by Britain this summer, the official told reporters.

He then spoke to the Munich conference, which draws top global leaders. Several years ago as a private citizen he reassured participants rattled by the Trump presidency: "We will be back."

On Friday, he told the virtual online audience: "America is back."

Democracies, not autocracies, offer the best path forward for the world, Biden said.

"We must demonstrate that democracies can still deliver for our people. That is our galvanizing mission. Democracy doesn’t happen by accident. We have to defend it. Strengthen it. Renew it. We have to prove that our model isn’t a relic of our history," Biden said.

He said the White House was reviewing a Trump administration cap on troops that can be deployed to Germany.

Russia, China challenges

Biden emphasized that major market economies and democracies must work together to tackle challenges posed by great-power competitors like Russia and China, and challenges ranging from nuclear proliferation to climate change and cybersecurity.

He pledged commitment to alliances that Trump had attacked, while attacking Russia and China.

"The United States is fully committed to our NATO alliance, and I welcome your investment in the military capabilities that enable our shared defenses," Biden said.

"An attack on one is an attack on all. That is our unshakeable vow."

Russia has tried to destabilize and undermine democracy in the United States and Europe and elsewhere, Biden said, asking allies to stand firm with Washington.

The Kremlin has repeatedly denied any such action.

"We have to push back against the Chinese government's economic abuses and coercion that undercut the foundations of the international economic system."

The Biden White House is reviewing China policy across an array of fronts, including its military buildup and trade policies, its actions in Hong Kong, treatment of minority Uighurs in Xinjiang and its handling of the coronavirus outbreak.

On the challenge posed by Iran's nuclear program, Biden will said the United States looks forward to re-engaging in diplomacy amid efforts to revive the Iran nuclear deal that Trump abandoned.

(Reporting by Andrea Shalal and Steve Holland; Editing by Peter Cooney, Heather Timmons and Howard Goller)