Updated

Senate Republican leader Mitch McConnell said Wednesday that his Democratic counterpart is barring any GOP changes to pending defense legislation because he "can't stomach a vote on Iran sanctions."

In a blistering speech on the Senate floor, McConnell railed against Democratic leader Harry Reid for changing Senate rules to limit the GOP's ability to filibuster and complained that Reid was jamming a comprehensive, $632.8 billion bill through the Senate without allowing any amendments.

The bill cleared one hurdle later Wednesday as the Senate voted 71-29 to move ahead on the legislation. Final passage was expected late Thursday.

Reid insists that he has no other choice to counter GOP delaying tactics on nominations and legislation, including the defense policy bill which attracted some 500 amendments before Thanksgiving.

McConnell, who spoke favorably about the defense bill, said Reid's motivation in preventing any amendments was to avoid a vote on Iran sanctions. The Obama administration has pleaded with Congress to hold off on a new round of tough penalties, fearing that it will undermine last month's nuclear deal with Tehran.

McConnell said the Nevada Democrat realizes "the administration would lose that vote decisively, and he knows that many members of his own caucus would vote alongside Republicans to strengthen those sanctions."

McConnell, R-Ky., called Reid's tactics a "short-term power grab" that could come back to haunt the Democrats if they find themselves in the minority.

The overall bill would authorize $552.2 billion for the regular budget plus $80.7 billion for conflicts overseas in the fiscal year that began Oct. 1. It represents a compromise worked out by the top Republicans and Democrats on the House and Senate Armed Services committees after a similar bill stalled in the Senate just before Thanksgiving.

The bill aims to stem the epidemic of sexual assaults in the military, cover the cost of combat pay for the nation's war-fighters, and fund new aircraft and ships. It reflects both the drawdown in Afghanistan and deficit-driven reductions in defense spending.

The House passed the measure last week on a strong bipartisan vote of 350-69.

Congress has passed the National Defense Authorization Act every year since the Kennedy administration.

The comprehensive bill would provide a 1 percent salary increase for military personnel, keep construction going on bases and an aircraft carrier in Virginia, and pay for the destruction of chemical weapons in Syria.

The legislation includes some two dozen provisions addressing the epidemic of sexual assault in the military. The Pentagon has estimated that 26,000 members of the military may have been sexually assaulted last year, though thousands were afraid to come forward for fear of inaction or retribution.

The bill would strip military commanders of their ability to overturn jury convictions, require a civilian review if a commander declines to prosecute a case and require that any individual convicted of sexual assault face a dishonorable discharge or dismissal. The bill also would provide victims with legal counsel, eliminate the statute of limitations for courts-martial in rape and sexual assault cases, and criminalize retaliation against victims who report a sexual assault.

The compromise adds another provision with strong bipartisan support that would change the military's Article 32 proceedings to limit intrusive questioning of victims, making it more similar to a grand jury.