Yanukovych defied an order by Yushchenko to dissolve parliament, telling an emergency session of the legislature that the president had made "a fatal mistake" and urging legislators to keep working.

He later threatened to force an early presidential election if the dissolution order was not rescinded.

Russia's foreign ministry called on all sides to seek a compromise, voicing concern over the crisis that is the culmination of a long-running battle between the ri val leaders.

The two met as thousands of chanting, flag-waving protesters gathered outside parliament to voice opposition to the president's decree.

Yushchenko announced the dissolution of parliament in a dramatic televised speech late Monday, calling snap legislative elections for May 27.

The decree came into force when it was published Tuesday in the official gazette, but Yanukovych called on parliament to stand fast.

The only possible way "of remedying the president's fatal mistake is waiting for a decision by the constitutional court," he told legislators in a session broadcast live on television.

"Until such a decision is made, the government should work as usual," he said.

Speaking later to supporters, Yanukovych said the president should understand that failure to rescind the dissolution would make presidential elections "inevitable."