Ukraine's governing coalition is on the brink of collapse after the pro-presidential "Our Ukraine-People's Self-Defense" party staged a walkout Tuesday.

President Viktor Yushchenko has threatened to dismiss parliament and call a snap election if a new governing coalition cannot be created in time.

The recent exchange of words and actions have plunged the country into yet more political turmoil, in what analysts believe the struggle for power between Yushchenko and Prime minister Yulia Tymoshenko is the root cause.

In last September's parliamentary elections, Yushchenko's bloc and Our Ukraine-People's Self-Defense party won 227 seats altogether in the 450-member parliament and formed a governing coalition led by Tymoshenko.

Yushchenko and Tymoshenko have since been engaged in a tug-of-war for power.

As the date draws near for the 2010 presidential election, in which the two rivals are likely to face off, the power struggle has reached boiling point, analysts say.

On Tuesday, the legislature passed amendments to the law on the cabinet of ministers and a series of bills that would weaken the power of the president.

The "Our Ukraine-People's Self-Defense" party accused Tymoshenko's bloc of colluding with the opposition Party of Regions during the votes and pulled out of the ruling coalition after an extraordinary meeting.

Yushchenko also described the move as a bid to establish a "dictatorship of the prime minister," saying "a political and constitutional coup d'etat has started in the parliament."

Rebuking Yushchenko's accusations, Tymoshenko said Wednesday the real reason the president "declared a war against me is to ensure his victory in the next presidential elections."