President-elect Dmitry Medvedev said some individuals could challenge his presidency after he takes office in May but that his "friendly" relationship with President Vladimir Putin would guarantee their productive cooperation.

Medvedev did not specify who might challenge him, though he said there may be "concerns" about his partnership with Putin, who has agreed to take over as prime minister under Medvedev.

"Like all the new power constructions, it will show its efficiency after some time," Medvedev told prominent journalist Nikolai Svanidze in excerpts of an interview published Thursday on the president-elect's web site. "People are going to test it for its durability. This is normal."

The interview will be the basis for a biography of Medvedev to be released in mid-May by the St. Petersburg publisher Amphora.

Kremlin insiders say one of the powerful clans of security officers that form the bedrock of Putin's power opposed Medvedev's ascent, while a competing clan backed Medvedev's election.

It was unclear whether Medvedev was referring to the ongoing clan wars when he told Svanidze that his doubters "will do what people in politics do, which is political maneuvering."

"But we are all grown-ups," Medvedev said. "We can handle it."

Medvedev said, however, that he was not opposed to former security service officers holding top government posts.

"If there are people who have worked in the security services running the country, they often employ others who have their same experience," Medvedev said. "These are people with whom they have worked. There is nothing wrong with that."

Medvedev said Putin's decision to accept the prime minister's position was unprecedented in Russian history.

"This is just something new for our country," Medvedev said. "In Russian history the head of the state -- regardless how he was called -- has never left to take a secondary post. He either retired or fell into disgrace."