The government of Ukraine does not rule out discussing snap elections with the opposition, a high-ranking official said ahead of a meeting of top European diplomats in Kiev Thursday.

"We have to hold negotiations," said First Deputy Prime Minister Sergei Arbuzov when asked by Ukrainian Channel 5 late Wednesday if he considers snap parliamentary and presidential elections a solution to the ongoing standoff by pro-EU demonstrators across the country.

Ukrainians should be allowed to choose their own future, U.S. Secretary of State John Kerry said Wednesday, after Kiev's decision to put a key EU pact on hold sparked mass street protests in the former Soviet state.

Kerry praised Moldova for initialing an EU agreement during a visit to that country, saying that "The United States believes deeply that European integration is the best road for both security and prosperity for Moldova."

German Foreign Minister Guido Westerwelle on Wednesday said the gates of Europe were still open for Ukraine, after mass protests against the government's decision to walk away from a deal with the European Union.

"The gates of the European Union are still open. Ukraine has to be on board in Europe and the offers from Europe are still valid," Westerwelle told reporters, before heading to the heart of the protests on Independence Square.

The United States and the European Union have taken a firm but cautious stance on Ukraine as it hangs in the East-West balance even while Russia has felt free to be more combative, analysts say.

In a declaration Tuesday, foreign ministers of the 28 NATO member states, including U.S. Secretary of State John Kerry, took a moderate line as mass protests continued in Kiev after the government abandoned a planned association accord with the European Union.

Ukraine's three post-Soviet former presidents voiced support on Wednesday for mass protests raging in the capital Kiev against the government's decision to reject a historic pact with the European Union.

"We express solidarity with the peaceful civic actions of hundreds of thousands of young Ukrainians," said a statement from Leonid Kravchuk, Leonid Kuchma and Viktor Yushchenko, and posted on Yushchenko's party website.

Russian Foreign Minister Sergei Lavrov on Wednesday accused NATO of interfering in Ukrainian affairs, saying he did not understand why it felt it had the right to do so.

"I do not understand why NATO adopts such statements," Lavrov said of a declaration Tuesday by the alliance calling for dialogue between the government and protesters angry at its decision to ditch an EU association accord.

Ukrainian Prime Minister Mykola Azarov on Wednesday called on the opposition to stop escalating tensions in the country's worst political crisis in a decade, at the first cabinet meeting since mass street protests began.

"I am announcing a call to stop an escalation of political tensions," Azarov said at the start of a government meeting as some 1,500 protesters sought to blockade the government headquarters amid a heavy police presence.

NATO foreign ministers called Tuesday on the Ukraine government and opposition to open a dialogue after President Viktor Yanukovych ditched an EU association pact, sparking violent street protests.

Unusually as the issue was not formally on the agenda, NATO said recent developments in the former Soviet state had been discussed and a declaration agreed.

Ukrainian Prime Minister Mykola Azarov apologized on Tuesday for a brutal police crackdown on Kiev protests over the weekend that drew firm Western condemnation and sparked even bigger rallies.

"On behalf of our government, I would like to apologize for the actions of our law enforcement authorities on Maidan (Independence Square)," Azarov told an emergency parliament session to chants of "resignation" from pro-EU opposition lawmakers.

The White House said Monday that it did not consider peaceful demonstrations in Ukraine as attempts at a coup, and called violent suppression of protests by police unacceptable.

"We certainty don't consider peaceful demonstrations coup attempts," said White House spokesman Jay Carney after Ukrainian Prime Minister Mykola Azarov said the protests bore all the hallmarks of a coup.