The For Reforms movement demanded earlier this month that authorities change the Constitution by next month.
The headquarters of the For Reforms movement said the deadline was April 10, otherwise mass protests that swept the capital, Bishkek, late last year would resume. The opposition is demanding the resignation of President Kurmanbek Bakiyev and early elections.
"I am calling on all political forces to open constructive dialogue. Civil confrontation is harmful to Kyrgyzstan," Kurmanbek Bakiyev said in a televised address to the nation.
Opposition rallies in November resulted in a new constitution, turning the country into a parliamentary republic, but two months later Bakiyev threatened to dissolve the legislature and parliament voted to change the Constitution back and restore presidential powers.
"The president expanded his authority and reestablished authoritarian clan rule in the country," For Reforms representatives said, adding they would join forces with a new opposition party, United Front for Kyrgyzstan's Decent Future, led by dismissed prime minister Felix Kulov.
A former political prisoner, Kulov came to power in March 2005 in an alliance with Bakiyev on the back of violent protests. But the new leadership was accused of failing to act on promises to curb corruption and raise living standards in the impoverished post-Soviet nation.
Kulov resigned along with his Cabinet amid street protests over the Constitution and lack of progress in the promised reforms in the Central Asian country. In January, President Bakiyev twice nominated Kulov for prime minister, but MPs rejected the candidacy.
