As President Joe Biden takes up crises from Iran to Myanmar to climate change, one aspect of his approach has been strikingly consistent -- seeking rock-solid cooperation with allies.

After one month in the White House, it may be too soon to speak of a "Biden doctrine" but he has quickly carried out a sharp reversal of the brash "America First" philosophy of his predecessor Donald Trump, who delighted in needling friendly leaders.

In his first international address, Biden vowed Friday before the virtual Munich Security Conference that he will be "in lockstep with our allies and partners."

"Let me erase any lingering doubt: The United States will work closely with our European Union partners and the capitals across the continent -- from Rome to Riga -- to meet the range of shared challenges we face," he said.

Biden has already rejoined the Paris climate accord and stopped the US exit from the World Health Organization, seeing global cooperation as crucial to his top priorities of fighting Covid-19 and climate change.

For his administration's long-awaited first move to jumpstart diplomacy with Iran, the State Department worked off a proposal by the European Union which offered to convene an informal meeting on a 2015 nuclear accord that is on the brink of collapse after Trump's withdrawal.

After Myanmar's coup, Secretary of State Antony Blinken similarly sought a joint front with partners, India and Japan, that have better relationships with the nation the United States wants to persuade.

Biden has also dumped Trump's plan to pull troops out of ally Germany, moved to resolve a payment rift with South Korea over US base support and opened joint consultations with Japan and South Korea, allies with tensions between them, to chart the way forward on North Korea.

On confronting a rising China and Venezuela's leftist leader Nicolas Maduro, the Biden policy is less a change from Trump than a promise to secure more international support.

"President Biden's major criticism of the Trump strategy here was not that he wasn't getting tough on China on trade but that he was doing so alone, while also fighting our allies and partners," one senior US official said after Biden spoke by phone with President Xi Jinping.

Biden by contrast has taken a symbolic distance from several allies who rallied behind Trump but whose policies are at odds with some of his administration's goals, including the leaders of Israel, Saudi Arabia and Turkey.

Seeking benefits from friends

Biden's pursuit of diplomacy is hardly a surprise. In a half-century career in Washington, he has prided himself on building relationships and explicitly put reviving alliances high on his campaign agenda.

A study last year involving Biden aides including Jake Sullivan, now his national security advisor, said that the United States will need to "regain the trust of US allies and partners" and assure them that policies and accords do not change drastically with each administration.

Biden's engagement has been immediate. One ambassador of a US ally based in Washington said with delight that he is in nearly daily contact, albeit virtually, with the administration; while Blinken joked in an interview with National Public Radio that the State Department was fortunate to be on "the family plan" for telephone bills.

Biden administration officials "have been spending these last few years looking forward to an opportunity to strengthen alliances, so I do think that this is very much a concerted effort," said Zachary Hosford of the German Marshall Fund of the United States.

Biden's engagement will be welcomed by leaders who "believed President Trump viewed alliances almost purely through a transactional lens," Hosford said.

But the experience of Biden's former boss, Barack Obama, shows not to overstate the value of alliances.

Obama was wildly popular with the European public but he still had heated, if polite, disagreements with allied leaders including over trade, fiscal policy, defense spending and the brutal wars in Libya and Syria.

Hosford expected Biden to choreograph statements with allies but said the administration could also encourage coordinated efforts, such as on sanctions against human rights violators.

"We can have a much greater effect, not only symbolically, but in cases where officials actually keep money overseas," he said.

"There's a lot of hard work to do because alliances are a means to an end -- not an end unto themselves."