ANKARA

U.S. Secretary of State Mike Pompeo on Monday said he is en route to Brussels to discuss Transatlantic cooperation with leaders of NATO and EU.

Pompeo will meet with Belgian Prime Minister and European Council President-elect Charles Michel, and NATO Secretary General Jens Stoltenberg, according to a statement released by the U.S. Department of State.

During his two-day trip, he will also exchange opinions with European Parliament President David Sassoli and European Commission President-elect Ursula von der Leyen, the statement added.

''We can do more together through meaningful, effective multilateralism,'' tweeted Pompeo at a time when other top U.S. officials also announced Washington's intention to take a tougher stance against Russia.

On Sunday, ahead of a bilateral meeting with the Ukrainian president this week, U.S. Vice President Mike Pence said the U.S. "will continue to stand with the people of Ukraine'' on security and territorial integrity matters, ''including Ukraine’s rightful claim in Crimea".

Pence, however, did not talk about reports that U.S. President Donald Trump is considering military aid cuts to Ukraine worth $250 million.

Russia annexed Crimea in 2014 despite the protest of UN, U.S., EU and many other countries.

U.S. Energy Secretary Rick Perry, after meeting Polish and Ukrainian officials in Poland's capital Warsaw, said on Saturday that Washington is planning to toughen sanctions on Russia because of its Ukraine policies.

Washington and its traditional European allies have been at odds with each other in their view of the Iran threat since Trump administration in 2018 backed out from a landmark Iran nuclear deal signed in 2015.

Trump has also been accusing the major European countries of waging an ''unfair'' trade war with the U.S. since his election in 2016.