Russian President Vladimir Putin will lead the ruling United Russia Party.
The move will help him continue his policies after he leaves the Kremlin to become prime minister next month.
Putin was elected chairman for a four-year term by the nearly six-hundred delegates at the party's congress.
Becoming head of United Russia enhances Putin's power base in the State Duma, the lower house of Russia's parliament. The party holds a two-thirds majority there.
Putin says he is ready to accept additional responsibility and to head United Russia.
Vladimir Putin, Russian President, said, "I'm accepting with gratitude the proposal of the party membership and leadership.
President-elect Dimitry Medvedev turned down a membership offer in the United Russia Party, saying the president should not be affiliated with any political party.
Medvedev says he supports Putin become party chairman. He says the outgoing president is already its informal leader after it won a majority in December's parliamentary elections.
Both he and Putin hope to improve coordination between the government and parliament.
Putin steps down on May 7th and will serve as prime minister during Medvedev's presidency.