Idaho Sen. Larry Craig refused on Thursday to resign from office despite a judge's ruling that denied his efforts to withdraw the guilty plea he entered in August in connection to an airport bathroom stall sex sting.

"I am extremely disappointed with the ruling issued today. I am innocent of the charges against me. I continue to work with my legal team to explore my additional legal options," Craig said, according to a statement released by his office.

"I will continue to serve Idaho in the United States Senate," the Idaho Republican said.

Earlier Thursday, Minnesota District Judge Charles Porter's decision was released by the court. Porter denied Craig's motion to withdraw his Aug. 1 guilty plea to a single misdemeanor charge of disorderly conduct.

• Click here to read a copy of the plea agreement (FindLaw.com)

• Click here to read a copy of the charges (FindLaw.com)

Guilty pleas often have a difficult legal barrier to overcome because of their voluntary nature. While Porter did not dismiss the case outright on its timeliness, he picked apart Craig's claims in a 27-page decision.

In his ruling, Porter said the case overwhelmingly fell against Craig.

"Because the Defendant's plea was accurate, voluntary, and intelligent, and because the conviction is supported by the evidence, the Defendant's conviction for disorderly conduct occurring on June, 11, 2007, in the men's public restroom at the Minneapolis-St. Paul International Airport in Bloomington, Hennepin County, Minnesota, is valid," Porter wrote, adding that Craig's "motion to withdraw his guilty plea is DENIED," Porter wrote.

• Click here to read the judge's order.

Craig has denied any wrongdoing in the June 11 incident, in which an undercover police officer alleged Craig was making hand and foot gestures signaling he wanted to engage in sex. Yet he entered a guilty plea to the disorderly conduct charge.

The incident remained out of the public eye, however, until a late August report in the Capitol Hill newspaper, Roll Call, uncovered Craig's legal problems.

That week, Craig announced his intention to resign from the Senate at the end of September, but he notably did not commit to a resignation. It later became clear why: Because he believed he had a shot at withdrawing his guilty plea.

Craig and his lawyers claimed that the conservative senator — who has fought allegations of homosexuality for most of his public career — was under extreme duress because the Idaho Statesman newspaper at the time was pursuing a separate story with new allegations of homosexuality.

Craig said Thursday he won't seek re-election, but he will strive to clear his name.

"As I continued to work for Idaho over the past three weeks here in the Senate, I have seen that it is possible for me to work here effectively," Craig said, adding that he believed its important for him to continue serving on the Appropriations, Energy and Natural Resources and Veterans Affairs committees — where he still remains, but has since been stripped of leadership positions.

"In addition, I will continue my effort to clear my name in the Senate Ethics Committee - something that is not possible if I am not serving in the Senate. When my term has expired, I will retire and not seek reelection. I hope this provides the certainty Idaho needs and deserves," Craig said.

Craig's legal woes caused consternation among his fellow Republicans, who already are facing an uphill battle in the 2008 elections with an unpopular president in office, an unpopular war, and other senior GOP senators taking their exits.

President Bush said he believed it would be the "right thing" for Craig to step down, and the Republican Senate leadership were vocally supportive of Craig's leaving the body. Craig also is facing an Ethics Committee inquiry.