The deployment's timing may help shape calculations of the United States and others in long-running standoffs with Iran and North Korea over their nuclear programs.

The precision-guided, 30,000-pound Massive Ordnance Penetrator, or MOP, is designed to wreck potential targets such as deeply buried nuclear facilities that are beyond the reach of existing bombs.

"Funding delays and enhancements to the planned test schedule have pushed the capability availability date to December 2010," Tara Rigler, a Pentagon spokeswoman, said in an email.