US Secretary of State Rex Tillerson on Thursday will make his diplomatic debut at a G20 gathering in Germany, where his counterparts hope to find out what "America First" means for the rest of the world.
Host nation Germany has billed the two-day meeting as a chance for the club of leading economies to discuss how to work together on challenges ranging from climate change to the Syrian war at a time of geopolitical upheaval.
But all eyes will be on America's top diplomat, whose maiden trip to Europe will bring him face-to-face with allies seeking reassurance that President Donald Trump will not upend decades of US foreign policy despite his fiery campaign rhetoric.
Tillerson will also have his first sitdown with Russian Foreign Minister Sergei Lavrov in Bonn, talks that will be closely scrutinised for any hint of a rapprochement as controversy swirls over White House ties to the Kremlin.
The pair will "discuss bilateral relations, which were taken into a dead end by the previous administration," a Russian foreign ministry spokeswoman said.
The high-level G20 gathering could also provide an opportunity for an encounter with Chinese Foreign Minister Wang Yi, whose attendance was only confirmed Tuesday.
The last-minute announcement came after Trump reaffirmed US adherence to the decades-old position that Taiwan is not separate from China, backtracking on earlier comments that cast doubt on the "One China" policy.
If former ExxonMobil boss Tillerson faces the daunting task of clarifying Trump's, at times, contradictory policy signals to a wary international community, he will not be doing it alone.
US Defence Secretary James Mattis is attending the second day of a NATO meeting in Brussels Thursday, while Vice President Mike Pence will be the highest-ranking US official participating in the Munich Security Conference from Friday.
"There are plenty of uncertainties about what they want, what they plan," a European diplomat said about the Trump administration. "We hope we'll get some clarity in the weeks to come."
- 'Your children's security' -
Speaking in Brussels on Wednesday, Mattis reaffirmed Washington's commitment to NATO after Trump last month branded the Western military alliance "obsolete".
But the former Marine also sternly rebuked member states for not paying their fair share, and warned that Washington would "moderate its commitment" unless they boost their spending.
"Americans cannot care more for your children's future security than you do," he said.
Looming large over this week's US diplomatic offensive is the scandal surrounding the resignation of Trump's national security advisor Michael Flynn.
He was forced to step down after less than a month in the job on allegations he discussed US sanctions over Moscow's involvement in the Ukraine conflict with a Russian official before taking office.
In Bonn, Tillerson will likely also face questions over Trump's commitment to the European Union after he rattled capitals on the continent with his praise for Britain's decision to quit the bloc and his prediction that other countries would follow suit.
The G20 event is being hosted by German Foreign Minister Sigmar Gabriel, a vocal critic of Trump's protectionist leanings who has warned that the world should brace for a "rough ride" under the billionaire politician.
"No country in the world can tackle the major international problems of our time alone," Gabriel said ahead of Thursday's talks.
The G20 grouping accounts for some 85 percent of the global economy and two thirds of the population.
Other high-profile diplomats attending the talks include Turkey's Mevlut Cavusoglu, the EU's Federica Mogherini, and Britain's Boris Johnson.
The meeting is a precursor to a G20 leaders' summit scheduled to take place in Hamburg in July, likely to be the first time Trump will meet Russian President Vladimir Putin in person.