Czech President Milos Zeman and the US ambassador to Prague have clashed over the leader's plan to travel to Moscow for a World War II victory anniversary, an event largely snubbed by Western leaders.

In a TV interview last week, US ambassador Andrew Schapiro questioned the staunchly pro-Russian Zeman's wish to be "probably the only EU head of state" to attend the May 9 parade on Moscow's Red Square marking the 70th anniversary of the Soviet Union's victory over Nazi Germany.

He added, however, that it was not up to him to tell the Czech president what to do.

Zeman is one of a handful of world leaders set to attend the event ignored by most Western leaders amid tensions over Russia's role in Ukraine.

In an interview on Sunday, Zeman said that the door to his official residence, Prague Castle, "will be closed" to Schapiro following his criticism.

"I can't imagine the Czech ambassador to Washington giving travelling advice to the US president," Zeman told the parlamentnilisty.cz news site.

"And I won't let any ambassador meddle in my plans to travel abroad," added the 70-year-old leftwinger, in office since 2013 as the first-ever directly elected Czech head of state.

The spat intensified when Czech leftwing Prime Minister Bohuslav Sobotka on Monday criticised Zeman's response and urged the president to adopt a "more professional approach to foreign policy."

In Washington, the US State Department said it understood "the desire to honour all those who sacrificed in World War II".

"And of course, each country can make its own decisions about attendance," said spokeswoman Marie Harf, adding: "We haven't decided about ours yet."

But she said now was not the time for "business as usual" with Moscow, stressing "the importance of unity with our European allies and partners in pressing Russia to stop fuelling the conflict in eastern Ukraine."

Most Western leaders have given Russian President Vladimir Putin the cold shoulder while German Chancellor Angela Merkel has promised to visit Moscow on May 10.

Besides Zeman, those known to be planning to attend the WWII commemoration in Moscow include Greek Prime Minister Alexis Tsipras and North Korea's Kim Jong-Un as well as the leaders of India, South Africa, Mongolia, Cuba and Vietnam.