SPOKANE, Wash. (AP) — The attorney for a man with extensive ties to white supremacists asked a judge to withdraw his client's guilty plea on Tuesday, hours before he was scheduled to be sentenced in connection with a plot to detonate a bomb at a Martin Luther King Jr. Day parade.

Kevin Harpham's attorney, Roger Peven, questioned whether the explosive device in question met the legal definition of a bomb. 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.

It was not immediately clear whether the judge would immediately act on the last-minute request or whether it would affect the timing of the sentencing if it is rejected.

Prosecutors had dropped charges of using a firearm in relation to a crime of violence and unauthorized possession of an unregistered explosive device. Under the plea deal, he faces a range of 27 to 32 years in prison. If he had been convicted, he could have faced up to life in prison.

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

The Jan. 17 parade drew a crowd of about 2,000 adults and children on a cold winter morning, and was forced onto an alternate route after the bomb was found. Harpham walked in the parade and took pictures of young black children and of a Jewish man who was wearing a yarmulke, prosecutors have said.

Prosecutors said Harpham acted alone. He was arrested March 9 at his rural home near Addy, Wash.

Harpham is an Army veteran who has extensive ties to white supremacist groups but no record of past crimes. The Southern Poverty Law Center, which tracks hate groups, has said that Harpham made more than 1,000 postings on a white supremacist website. The center also has said that Harpham belonged to a neo-Nazi group.

His lawyers have said Harpham had not been recently employed.

He has remained in the Spokane County Jail without bail since his arrest.