MOSCOW — Mikhail Prokhorov, one of Russia's richest tycoons and the owner of the New Jersey Nets basketball team, said today he will run against Prime Minister Vladimir Putin in the March presidential election.

Prokhorov has been cautious not to cross Putin's path in the past, but the billionaire may pose a serious challenge to Putin, whose authority has been dented by alleged widespread fraud during Russia's Dec. 4 parliamentary election.

Putin's party won only about 50 percent of that vote, compared to 64 percent four years ago, and the fraud allegations have allowed opposition parties to mount massive anti-Putin protests in Russia.

BRUSSELS — NATO will permanently shut down its military training mission in Iraq and withdraw all of its soldiers from the country by Dec. 31, the alliance said today.Talks on extending the mission had stalled over NATO’s request for legal immunity for the foreign trainers, an issue that earlier ended plans to keep a residual U.S. military presence in the country.