Updated

Guerrilla attacks in Iraq suggest insurgents are trying to create strife among Iraqis as a means toward frustrating U.S. interests there, but it's not working, Defense Secretary Donald H. Rumsfeld (search) said Sunday.

Some attacks aim to foster interethnic and interreligious conflict, he said. Others are strikes against the newly formed security services, with the apparent aim of persuading Iraqis not to join.

"They're killing Iraqis. The Iraqi people don't like it," Rumsfeld said.

"Instead of responding by acquiescing, we see volunteers are still in line to join the police. They're still in line to join the Army. They're leaning forward. They're taking losses, and God bless them for it."

Rumsfeld said he believes a recently intercepted letter, purportedly from a terrorist organizer connected to the Al Qaeda terror network, is authentic. The letter writer, believed to have been Abu Musab al-Zarqawi (search), wrote of efforts to cause a civil war between the two major Muslim sects, the long-dominant Sunnis and the majority Shiites.

Rumsfeld spoke to reporters during a refueling stop at Shannon, Ireland, while traveling to Kuwait to visit U.S. troops in the Persian Gulf (search) region. He described the resistance fighters as a mix of former members of Saddam's regime, criminals and guerrillas of Al Qaeda and other groups.

As the U.S.-led coalition that ousted Saddam Hussein tries to turn over security matters to Iraqis and reduce its military presence in the country, Rumsfeld predicted U.S. troops increasingly would see action only in support of Iraqi forces in hot spots of guerrilla activity.

"It will vary in different parts of the country," Rumsfeld said. "In one section of the country, the military commander will make a judgment they can move back and put the Iraqi forces out front, and that will stand permanently. It may also be in some parts of the country that won't happen, and they'll make a judgment ... they need to press back in and support the Iraqi security forces. You'll see that ebb and flow for period of time."

Military officials have offered no firm date on when most U.S. troops will leave Iraq. The services are planning for deployments several years ahead.

Even now, the Pentagon has under way one of the largest troop rotations in U.S. history as up to 200,000 soldiers will have moved in or out of Iraq before May.

At the refueling stop in Ireland, Rumsfeld's party by chance came upon members of an Oklahoma National Guard unit who also were making a refueling stop while en route to begin a yearlong tour in Iraq.

Many of the soldiers, part of an engineering battalion that will help in reconstruction projects, swarmed around the defense secretary.

Speaking to the troops, Rumsfeld compared the U.S. effort in Iraq to that during the Korean War and suggested that Iraqi cities may someday be as well-off as South Korea capital, Seoul.

He also thanked the guardsmen for their service.

"Everyone here is a volunteer. Everyone here is someone who decided to step forward and serve their country. It's noble. It's tough. We are deeply appreciative," he said.

"Hooah," the troops answered in unison, the Army's shout of approval.

In Kuwait, Rumsfeld met briefly with the prime minister, Sheik Sabah Al Ahmed Al Sabah (search).

Rumsfeld's tour also will take him to Tashkent, Uzbekistan, his third visit in two years in the Uzbek capital. The Uzbek Foreign Ministry said Saturday he also plans visits to neighboring Kazakhstan and Afghanistan.