BERLIN, June 5 (Xinhua) -- Richard Grenell, the new U.S. ambassador to Germany, was criticized sharply on Monday for breaking diplomatic protocol in an interview with the right-wing online portal Breitbart.

The German government has demanded that Washington formally clarify how Grenell's comments are to be interpreted, a Foreign Office spokesperson told the press.

In the interview published Sunday, the 51-year-old former communications consultant vowed to "support other conservatives throughout Europe".

He also said the election of U.S. President Donald Trump had "empowered" citizens to rise up against undemocratic political elites on the continent and chastised Germany for failing to meet NATO spending goals in spite of its national wealth.

Grenell, formally appointed as U.S. ambassador by Trump only in May, has already caused eyebrows to be raised repeatedly in his host country by publicly interfering in domestic politics.

Earlier, he had asked German companies to "wind down their operations immediately" in Iran after Washington decided to withdraw from the nuclear agreement signed by the Middle Eastern nation, China, Russia, Germany, France, Britain and the United States in 2015, a move that has been widely condemned.

Several German policymakers said on Monday that Grenell's latest comments had crossed the red line and called for Berlin to insist on his replacement by a more qualified candidate.

European citizens will not allow themselves to be told by a vassal of Trump how they should cast their votes. A U.S. ambassador who interferes in democratic debates to this extent is not suited to his job, Thorsten Schaefer-Guembel, a Social Democratic Party member of Parliament, said in a tweet.

Martin Schulz, former leader of the party and head of the European Parliament, said it was the duty of ambassadors to represent their countries as a whole, rather than specific political movements. Schulz likened Grenell's behavior to that of a "right-wing extreme colonial officer".

Another deputy leader of the parliamentary faction of the party, Ralf Stegner, also expressed astonishment at Grenell's lack of tact.

Drawing attention to the deterioration of relations between Berlin and Washington over several areas, Stegner said Trump's "anti-European views" were already "bad enough" without the U.S. ambassador adding fuel to the fire.

Speaking to Die Welt daily, Elmar Brok, a senior Christian Democratic Union politician who is also a member of the European Parliament and foreign policy expert, warned that Grenell's political intervention could backfire.

He said many of the European parties the ambassador had sympathized with favored closer relations with Russia.

Even if Grenell's attempts proved futile, Sevim Dagdelen, leader of the Left Party's parliamentary faction, said Grenell had "outed himself" in the Breitbart interview as a "regime-change officer installed by the president".

Dagdelen urged German Foreign Minister Heiko Maas to summon Grenell and push back against his political meddling.

A Foreign Office spokesperson said Grenell was scheduled to have his inaugural meeting at the department on Wednesday and would have an opportunity to clarify his statements.