ALEXANDRIA, Va. — A federal judge ruled Monday that prosecutors can use a confession by a man charged with joining al-Qaida and plotting to assassinate President Bush, despite defense claims that the confession was obtained through torture.

The ruling came after a six-day hearing in which Ahmed Omar Abu Ali testified that Saudi Arabian security officers whipped his back, kicked him in the stomach and pulled on his beard to obtain a confession.

U.S. District Judge Gerald Bruce Lee issued a one-page ruling and said he would explain his reasoning in a forthcoming order.

Abu Ali's lawyers wanted the confession tossed out and the entire case dismissed. But Lee's ruling means the trial will go forward this week, with jury selection today and opening statements as early as Thursday.

During the hearing, the judge reviewed photographs of Abu Ali's back that showed thin lines or scars that the 24-year-old said were proof of a flogging. Prosecutors argued the faint markings could have been caused by anything and might have been self-inflicted to bolster a torture claim.

Prosecutors also argued that Abu Ali's confession was voluntary, citing the 13-minute videotape in which he made jokes and pantomimed the use of an assault rifle.

In the confession, Abu Ali said he joined al-Qaida because he hated the U.S. for its support of Israel. He said he discussed numerous potential plots with his al-Qaida cell members, including plans to assassinate Bush, conduct a Sept. 11-style attack using planes hijacked from outside the United States, establish an al-Qaida cell inside the U.S. and free Muslim prisoners held at Guantánamo Bay.

Abu Ali was born in Houston and graduated from an Islamic high school in Virginia in 1999. He is charged with joining al-Qaida while in Saudi Arabia.

Abu Ali was arrested in June 2003 while taking exams at the Islamic University of Medina. He said he was tortured the next day after he refused to speak with interrogators.

Abu Ali also confessed to FBI agents in September, but prosecutors have acknowledged that confession is invalid because they disregarded Abu Ali's request for an attorney.

Abu Ali is charged with conspiracy to assassinate the president, conspiracy to commit aircraft piracy, providing material support to al-Qaida and other crimes.