Col. Tara Osborn, the judge at Hasan's court martial, did not rule on his request as jury selection began, the Austin American-Statesman began.
Hasan, a psychiatrist, is acting as his own lawyer. He has said he will be represented by former U.S. Attorney General Ramsey Clark if Osborn allows him to use a defense that he was justified in gunning down soldiers at Fort Hood to prevent unlawful violence to the Taliban in Afghanistan.
During Tuesday's hearing, Hasan said he believes the Army uniform "represents an enemy of Islam."
"I can't take any pride in wearing this uniform," Hasan said. "I want the panel to know that, that I am being forced to wear it."
Hasan, 42, born in Virginia to Palestinian immigrant parents, joined the Army after high school and attended college and medical school while in the military. Relatives said he became more devout after his parents died although a cousin said he did not appear to be anti-American.
In 2009, a month before he was scheduled to be deployed to Afghanistan, Hasan allegedly opened fire on soldiers at Fort Hood, killing 13 and wounding 29.
Clark, who served as President Lyndon Johnson's attorney general from 1967 to 1969, played an important part in drafting the 1965 Voting Rights Act. He has since become known as a radical and has represented many controversial people, including Saddam Hussein and Serbian leader Slobodan Milosevic.