Ukrainian President Viktor Yushchenko has ended a shaky political truce with Prime Minister Viktor Yanukovich by announcing the dissolution of parliament -- a move that has positioned the rivals in a bitter standoff.

The announcement ended a reluctant relationship that Yushchenko entered into last August when he appointed rival Viktor Yanukovich as prime minister.

In an emergency session of parliament Tuesday, Yanukovich said the president was making a "fatal mistake" by calling for a snap parliamentary poll on May 27, reports the BBC.

Yanukovych also threatened to try and force a presidential election if Yushchenko persisted in his plans.

Backed in parliament by a three-party coalition, Yanukovich said the 450-seat legislature would carry on until a ruling was made by the Constitutional Court on the validity of Yushchenko's latest move.

In total, 53 members asked the court to strike down Yushchenko's decree.

But Yushchenko stood firm Tuesday, reiterating that his position was final.

"The main issue discussed at the meeting was to ensure strict implementation of the decree on an early election," the president's press service said.

"Viktor Yushchenko, as commander-in-chief of Ukraine's armed forces, also stressed he would allow no use of force in the country."

Yanukovich's 2004 presidential 'victory' was met with large protests that accused the government of fixing the votes.

Yushchenko, who was left disfigured after surviving dioxin poisoning, eventually won a court-ordered rerun of the vote and became president.

However, Yanukovich made a comeback last year when his party won the majority in the parliamentary election.

That victory forced Yushchenko to name Yanukovich prime minister in a coalition government.

Yushchenko said he's calling the early election because, he alleges, Yanukovich has attempted to undermine his presidency. He is accusing him of violating an agreement they signed that outlined policy on domestic and foreign policies.

He also blames Yanukovich for poaching 11 lawmakers that were previously allied with his pro-Western government.

Protests

In protest, supporters of pro-Russian Yanukovich massed in front of Parliament Tuesday. The scene resembled a smaller version of the 2004 Orange Revolution demonstrations -- except this time the support was behind Yanukovich.

"The decree is not just a mistake. It is aimed against the country, the Ukrainian people," Yanukovich told supporters in the camp, Reuters reported. "The solution can be found only at the negotiating table, through compromise, not by violating the constitution."

Yushchenko supporters countered with a protest in Kyiv's main Independence Square.

The president has taken a risky move with the early election calls as polls suggest he would finish third -- behind Yanukovich and business tycoon Yulia Tymoshenko -- if votes were cast today.

With files from The Associated Press