Trump's election dismayed many European leaders, who see him as dangerously naive about the disruptive threat posed by Russia and fear his victory will inspire Europe's own far-right populist parties.

The new US leader has lavished praise on Britain's decision to leave the European Union and is reportedly planning to nominate Ted Malloch, a businessman who recently compared the bloc to the Soviet Union, as US ambassador to the EU.

Since his election, Trump has toned down some of his criticism of America's NATO allies in Europe, but he has shown no enthusiasm for the 28-member political union.

So Mogherini arrived in Washington on a delicate mission to build a working relationship with the novice administration, and began by meeting Secretary of State Rex Tillerson.

The Texas oilman, a former head of US energy giant ExxonMobil and a holder of Russia's Order of Friendship medal, hosted her at the State Department for what Mogherini later described as a "fruitful meeting."

"There are many files on which the EU and the US have an interest to closely cooperate," Mogherini said. Her office said the pair discussed counterterrorism strategy, relations with Russia, the Iran nuclear deal and the crises in Ukraine and Syria.

Trump has said he wants to mend ties with Russia's President Vladimir Putin. Europe fears he will take a soft line on Russia's intervention in Ukraine.

After her talks with Tillerson, Mogherini was due at the White House to meet National Security Adviser Michael Flynn -- another strong advocate of closer Russian ties -- and Trump's son-in-law and senior adviser Jared Kushner.