U.S. and Iraqi troops launched an operation in western Iraq to clear insurgents from a suspected safe area used to make car and roadside bombs, the military said Wednesday.

The campaign came as President Bush defended his Iraq policy by releasing a new war strategy, saying more Iraqi security forces are taking the lead in battle but adding that it is still uncertain when U.S. forces can withdraw.

About 1,500 U.S. Marines from the 13th Marine Expeditionary Unit, 500 U.S. soldiers and 500 Iraqi soldiers were taking part in Operation Iron Hammer near Hit, 85 miles west of Baghdad, a U.S. Marine statement said. The forces would concentrate efforts in the Hai Al Becker region, where U.S. and Iraqi troops rarely patrol, it added.

"The Hai Al Becker region is suspected to be an Al Qaeda in Iraq safe area and base of operations for the manufacture of vehicle car bombs, roadside bombs," the military said.

It added that the area is believed to be a stopping point for insurgents traveling down the Euphrates River from Syria into Iraq.

Meanwhile, in the central town of Baqouba, unidentified gunmen opened fire on a minibus early Wednesday, killing nine construction workers and wounding two, police said.

Following a new wave of kidnappings in which five Westerners were abducted since the weekend, German Chancellor Angela Merkel vowed that her government will "not let ourselves be blackmailed" by those who took a German archaeologist hostage.

"The government is doing everything in its power to bring the German citizen and her driver as soon as possible to safety," Merkel said.

Kidnappers have threatened to kill Susanne Osthoff and her Iraqi driver, who were kidnapped Friday, unless Germany halts all contacts with the Iraqi government. German TV station ARD showed images of what appeared to be Osthoff and her driver blindfolded on the floor beside armed and masked militants.

The other four abducted Westerners were members of Christian Peacemaker Teams, a group that has had activists in Iraq since October 2002. The group listed those abducted as Tom Fox, 54, of Clearbrook, Va.; Norman Kember, 74, of London; and James Loney, 41, and Harmeet Singh Sooden, 32, of Canada.

On Tuesday, Al-Jazeera broadcast video of the four men held by a previously unknown group calling itself the Swords of Righteousness Brigade. The group claimed they were spies working under the cover of Christian peace activists.

Christian Peacemaker Teams said it was saddened by the videotape of their workers, who the statement said were working against the occupation of Iraq.

"We are angry because what has happened to our teammates is the result of the actions of the U.S. and U.K. government due to the illegal attack on Iraq and the continuing occupation and oppression of its people," the group said.

"We are some of the few internationals left in Iraq who are telling the truth about what is happening to the Iraqi people. We hope that we can continue to do this work and we pray for the speedy release of our beloved teammates."

Loney, a community worker, was leading the Christian group's delegation in Iraq.

A German newspaper, the Neue Osnabruecker Zeitung, reported that Osthoff had received a kidnap threat last summer from extremists linked to Al Qaeda in Iraq leader Abu Musab al-Zarqawi and that U.S. soldiers brought her from Mosul to Baghdad for her own safety.

Lt. Col. Barry Johnson, a U.S. military spokesman, said he was unaware of the report but if true, such a move would have been with the knowledge of the German government and "we would ultimately leave it to them" to comment.

Germany has ruled out sending troops to Iraq and opposed the U.S.-led war, but it has been training Iraqi police and military outside the country.

Six Iranian pilgrims were seized Tuesday near a Shiite religious shrine north of Baghdad, police said. Iranian television reported that all were freed Tuesday night.

The latest attacks are part of a new wave of kidnappings police fear is aimed at disrupting the Dec. 15 parliamentary elections.

Iraq was swept by a wave of kidnappings and beheadings of foreigners in 2004 and early 2005, but such attacks have dropped off in recent months as many Western groups have left and security precautions for those who remain have tightened.

Insurgents, including Al Qaeda in Iraq, have seized more than 225 people, killing at least 38.

It was unclear whether the recent kidnappings were the work of a single group or simply coincidental. However, police believed they may be part of an insurgent campaign to discredit the government and disrupt the elections.

"Terrorists will try to destabilize the situation during the election period" in order to discourage people from voting, police Maj. Falah Mohammedawi said. "They will try to do this through kidnappings, assassinations and threats to citizens. We have our complete security plan to confront this."

U.S. and Iraqi officials hope a big turnout in the election will undermine the insurgency and improve chances for the United States and its partners to begin reducing troop levels in Iraq next year.

Facing criticism and impatience about the conflict, the White House released a 35-page plan titled "Our National Strategy for Victory in Iraq."

The plan says increasing numbers of Iraqi troops have been equipped and trained, a democratic government is being forged, Iraq's economy is being rebuilt and U.S. military and civilian presence will change as conditions improve.

Along with the report, Bush made a personal appeal to shore up wavering support for the war in remarks Wednesday at the U.S. Naval Academy in Annapolis, Md. — the first in a series of speeches between now and the parliamentary elections.