IMPEACH BUSH

(05-21) 04:00 PDT Baghdad -- Six U.S. soldiers and an interpreter were killed Saturday when a bomb exploded near their position in western Baghdad, the U.S. military reported Sunday, underscoring the heightened vulnerability of U.S. forces as they increase their presence in the capital.

A seventh U.S. soldier was killed by a roadside bomb Saturday in Diwaniyah, about 100 miles south of Baghdad, the military said. Two soldiers were wounded in that attack.

The deaths raise to 71 the number of U.S. service members killed this month.

The rising death toll comes as thousands more U.S. and Iraqi troops are engaged in a high-profile operation to improve security in the capital. U.S. officials warned when they announced the new plan in mid-February that putting as many as 25,000 more U.S. troops in the urban environment would raise their exposure and vulnerability, and that higher casualty rates were expected.

Military deaths have been rising since fall, and the first half of this year has already been deadlier than any six-month period since the war began more than four years ago.

According to iCasualties.org, 531 U.S. service members have been killed since Dec. 1, an average of more than three deaths a day. In all, at least 3,421 members of the U.S. military have died since the beginning of the Iraq war in March 2003.

The troops killed Saturday in Baghdad were part of an operation searching for weapons caches and bomb-making materials in the western part of the city over the past week "to aid in providing a more secure and safe environment for the Iraqi people," the military said.

In an unrelated development, U.S. forces over the weekend killed a man they said was the mastermind of a well-planned guerrilla assault in January in which English-speaking gunmen posing as Americans drove into a government compound in the southern holy city of Karbala, killed a U.S. soldier, then abducted four other U.S. soldiers who were later killed.

Azhar al-Dulaimi was killed in a raid on a building north of Sadr City, a large Shiite district in the capital, Maj. Gen William Caldwell, the U.S. military's top spokesman, said Sunday. Al-Dulaimi initially appeared to surrender, Caldwell said, but was shot while attempting to grab a soldier's gun and died en route to the hospital.

Al-Dulaimi was linked to the Karbala attack by fingerprints found at the scene, Caldwell said, adding that other evidence showed al-Dulaimi was trained by Iranian spies and the Lebanese Shiite movement Hezbollah.

Meanwhile, more than two dozen Iraqis were reported killed by roadside bombs, suicide attacks, mortar strikes and other violence Sunday. In addition, Iraqi national police reported finding 32 bodies Sunday: 22 in Baghdad, six in Mahmudiya, about 15 miles south of the capital, and four in the northern city of Mosul. An Iraqi police official in Baghdad, who was not authorized to speak on the record, said Interior Ministry forces clashed with insurgents who were spotted digging trenches in Dora, a Sunni Arab neighborhood in south Baghdad, and killed 14 in an ensuing firefight.

The U.S. military said it killed eight insurgents and arrested 34 in separate operations in Karmah, a Sunni area about 20 miles west of Baghdad, and in an area southwest of the capital. Also Sunday, the country's Sunni vice president spoke out against a proposed oil law, clouding the future of a key benchmark for assuring continued U.S. support for the government.

In recent months, U.S. officials have been stepping up pressure on Iraq's religious and ethnic parties to reach agreements on political and economic initiatives to encourage national reconciliation and end the fighting.

Progress in meeting those benchmarks is considered crucial to continued U.S. support for Prime Minister Nouri al-Maliki's government at a time when Democrats in Congress are pressing for an end to the war. Those benchmarks include enactment of a new law to manage the country's vast oil wealth and distribute revenues among the various groups.

But prospects for quick approval received a setback Sunday, when the country's Sunni vice president said in Jordan that the proposed legislation gives too many concessions to foreign oil companies.

"We disagree with the production-sharing agreement," Tariq al-Hashemi said at an international conference hosted by the Geneva-based World Economic Forum. "We want foreign oil companies, and we have to lure them into Iraq to learn from their expertise and acquire their technology, but we shouldn't give them big privileges."

The bill also faces opposition from the Kurds, who have demanded greater control of oil fields in Kurdish areas.

Iraq's Cabinet signed off on the oil bill in February and sent it to parliament, a move the Bush administration hailed as a major sign of political progress in Iraq. But parliament has yet to consider it.

Al-Hashemi is among three leaders of a Sunni bloc that controls 44 seats. Together, the Kurds and the Sunnis have enough legislative muscle to delay passage of the measure, which is likely to draw opposition from some Shiite lawmakers, too.

In another political setback, the leader of Iraq's largest Shiite party, Abdul-Aziz al-Hakim, has been diagnosed with lung cancer and was headed to Iran for treatment, party officials said Sunday. Al-Hakim's absence is likely to create disarray in his Supreme Islamic Council in Iraq -- a Shiite party the United States is counting on to push through benchmark reforms.

The Associated Press contributed to this report.

This article appeared on page A - 6 of the San Francisco Chronicle