MOSCOW (AP) — Russia's highest court ruled Thursday to free the jailed business partner of former oil tycoon Mikhail Khodorkovsky about three months early, but left in place a back tax claim of 17 billion rubles ($500 million) against Khodorkovsky that will in effect prevent him from returning to Russia.

Khodorkovsky was pardoned in December by President Vladimir Putin in December and put directly on a plane to Berlin. Now his partner Platon Lebedev is to walk free.

Both men spent more than 10 years in prison in a case seen as revenge against Khodorkovsky for challenging Putin's economic and political power in the early years of his presidency.

Khodorkovsky has said he would not return to Russia as long as the back tax claim remained in force, since it could prevent him from leaving the country again.

The Supreme Court ruled to reduce Lebedev's prison sentence to 10 years, six months and 22 days. Since Lebedev was arrested on July 2, 2003, this means he should be released immediately from a prison in the northwestern Arkhangelsk region.

But the court ruled that there were no grounds to remove the back tax claim against Khodorkovsky.