The top U.S. commander in Iraq predicted on Thursday that the size of the U.S. fighting force will shrink this year, although he said he had not made new recommendations to his Pentagon bosses on the size and timing of any cuts.

Army General George Casey (L) speaks as U.S. Secretary of Defense Donald Rumsfeld watches during their joint news conference at the Pentagon in Washington June 22, 2006. [Reuters]

"I'm confident that we'll be able to continue to take reductions over the course of this year," Army Gen. George Casey told a Pentagon news conference with Defense Secretary Donald H. Rumsfeld at his side.

Rumsfeld said Casey had not yet had sufficient time to consult with the new Iraqi government, but that in any case the size of the U.S. force is likely to rise and fall in coming months, depending on political and security conditions.

"It will very likely not be a steady path down," Rumsfeld said. "It could very likely be a drawdown with an increase." Noting that there now are 126,900 U.S. troops in Iraq, he said: "It could very well go back up at some point. It very likely will go down and up and down and up depending on the circumstances and depending on the need."

Casey, who said more than once last year that he expected to see "fairly substantial" U.S. troop reductions during spring and summer of 2006, noted that the force has dropped from about 138,000 in March to 126,900 now.

"Whether that's 'fairly substantial' enough, I'll leave to your judgment," he said. "As I said, I think there will be continued gradual reductions here as the Iraqis take on a larger and larger role."

Casey also said that members of the Sunni insurgency have been reaching out to the new Iraqi government, giving U.S. military commanders opportunities to forge communications with the resistance groups.

Casey said the U.S. military and the Iraqi government "have several different strands of contacts going on, and there are opportunities in that regard we just haven't had before." He did not elaborate. He also said the insurgency has grown more complex in recent months, and he complained that it has been assisted by Iranian special operations forces who provide bomb materials, weapons and training to Shiite extremists in southern Iraq.

"They are using surrogates to conduct terrorist operations in Iraq both against us and against the Iraqi people," Casey said. "It's decidedly unhelpful." He added there has been a "noticeable increase" in the problem since January, but he could not quantify it, Casey also said

Iran has become the main source of materials to make makeshift roadside bombs that regularly kill U.S. troops as well as Iraqis. "Those primarily come from Iran," he said. "We're seeing attacks and we're finding more of them. So it's coming in from, we believe, Iran."

The Republican-controlled Senate on Thursday soundly rejected two Democratic attempts to urge withdrawal of U.S. troops from Iraq, including an amendment to begin pulling out by the end of the year. GOP lawmakers accused the Democrats of wanting to abandon Iraq before the mission is complete, while Democrats said it is time for changes in Bush's failed Iraq strategy.

Asked about the wisdom of setting a fixed date for the start of a U.S. troop withdrawal, Casey said he opposed that approach.

"I feel it would limit my flexibility," he said. "I think it would give the enemy a fixed timetable. And I think it would send a terrible signal to a new government of national unity in Iraq that's trying to stand up and get its legs underneath it."