Boris Yeltsin nominated acting Prime Minister Sergei Kiriyenko to take over the post permanently and warned today he would disband parliament if legislators fail to approve his choice.

"I'm not trying to scare you," Yeltsin said in remarks directed at the opposition-dominated parliament. "I simply tell you as the president - save time. Make a fast approval."Gennady Seleznyov, a Communist who is speaker of the Duma, criticized the president's heavy-handed approach, but said parliament would probably endorse Yeltsin's candidate. A Duma vote tentatively was planned for April 3.

If the Duma rejects Yeltsin's candidates for prime minister three times, then the president must disband the Duma and call new parliamentary elections.

"Don't make another round of confrontation," Yeltsin warned the Duma, according to the ITAR-Tass news agency. "I will show no leniency."

Yeltsin said he supported Kiriyenko's plans to speed up and broaden free-market reforms, which have been hindered by massive government inefficiency and corruption.

"The plans are serious. That is what we need - to shake up reforms. The reforms have slowed down a little bit," he said.

Yeltsin stunned the country Monday by dismissing longtime Premier Viktor Chernomyrdin and the entire Cabinet without warning. He complained that reform efforts were in danger because many Russians had failed to see any improvements after years of economic and social decline.

In a radio address today, the president hailed Kiriyenko as a skilled professional who could work with various factions. The president shrugged off concerns that the 35-year-old Kiriyenko, a former oil company executive whose government experience consists of seven months in the Oil Ministry in the previous administration, was too young for the job.

"Professionalism and energy aren't determined by the date of birth," he said. "The essential thing is that a man knows his job, has fresh ideas and unorthodox approaches and knows how to reach his goals."

Nevertheless, Kiriyenko is expected to face a tough fight for approval in parliament, which is dominated by Communists and nationalists.

Seleznyov, the Duma speaker, said Yeltsin's threats were unnecessary.

"We don't need such reminders. We know quite well what is written in the constitution," he told reporters.