Spokane County Sheriff, File, Associated Press
FILE - This undated file photo provided by the Spokane County Sheriff shows Bombing Kevin William Harpham, who has pleaded guilty in connection with a plan to detonate a bomb at a Martin Luther King Jr. Day parade in Spokane, Wash., on Jan. 17, 2011. Harpham's attorney asked a judge to withdraw his client’s guilty plea just before he was scheduled to be sentenced Tuesday, Dec. 20, 2011.

SPOKANE, Washington — A judge on Tuesday rejected a last-minute request from a man who wanted to withdraw his guilty plea in a Martin Luther King Jr. Day parade bomb plot, just hours before his scheduled sentencing.

The lawyer for Kevin Harpham had questioned whether the explosive device in question met the legal definition of a bomb, saying the defense team had an expert who would testify that the device was not "an explosive bomb."

Harpham told a judge in September that he placed a pipe bomb loaded with poison-laced metal along the parade route in Spokane, Washington, on Jan. 17 as an attempt to commit a hate crime. It was discovered and disabled before it could explode.

Harpham previously agreed to a plea deal charging him with attempted use of a weapon of mass destruction, and the hate crime of placing the bomb in an effort to target minorities.

Under the plea deal, he faces 27 to 32 years in prison. If he had been convicted, he could have faced up to life in prison.

The parade drew a crowd of about 2,000 adults and children and was forced onto an alternate route after the bomb was found. Harpham walked in the parade and took pictures of black children and of a Jewish man wearing a yarmulke, prosecutors have said.

Prosecutors said Harpham acted alone. The Army veteran was arrested March 9 at his rural home.

The Southern Poverty Law Center, which tracks hate groups, has said Harpham made more than 1,000 postings on a white supremacist website. The center also has said Harpham belonged to a neo-Nazi group.

Harpham has no record of past crimes. He has remained in the jail without bail since his arrest.