The pro-Western party of Ukraine's president has announced that it is officially going into opposition.
Pro-democracy youth have been protesting outside parliament
The move follows months of political turmoil caused by a general election in March in which no party won a majority.
A pro-Russian coalition was formed earlier this month when an alliance of parties which supported the Orange Revolution collapsed.
Thousands of protesters have gathered outside the parliament building, according to local TV reports.
The BBC's Helen Fawkes in Kiev says the announcement means that the Our Ukraine Party, led by Viktor Yushchenko, will link up with some of its former Orange allies who are already in opposition.
The pro-Russian coalition is likely to find it difficult to govern, our correspondent says. It only has a small majority and is made up of parties with diverse interests.
It also means that Ukraine's political uncertainty looks set to continue.
The statement was made to a relatively calm parliament. Last week there were rowdy scenes as a number of MPs physically attacked each other.
The governing coalition has also nominated Viktor Yanukovych to be appointed prime minister.
Mr Yanukovych, who leads the largest party, lost the 2004 presidential election in which allegations of vote-rigging sparked the Orange Revolution.