(Adds claim of responsibility for Arbil attack, Iraqi national security adviser)

By Ibon Villelabeitia

BAGHDAD, May 9 (Reuters) - U.S. Vice President Dick Cheney pressed Iraq's leaders on Wednesday to move without delay to reach power-sharing accords that Washington says are vital to ending sectarian violence.

Cheney's unannounced visit to Iraq, part of a Middle East tour, signaled growing U.S. impatience at Iraq's slowness in passing laws on oil distribution and other key measures as U.S. military commanders build up troops to secure Baghdad.

Cheney said talks also centered on the crackdown in the capital, involving the deployment of 30,000 extra U.S. troops in what is seen as a last-ditch effort to stave off civil war between majority Shi'ites and once-dominant Sunni Arabs.

"I emphasized the importance of making progress on the issues before us, not only on the security issues but also on the political issues that are pending before the Iraqi government," Cheney said.

Prime Minister Nuri al-Maliki, a Shi'ite, said his government was committed to restoring order, achieving national reconciliation and ensuring all Iraqis were able to share in the country's vast oil wealth.

Underscoring Iraq's huge security challenges, a suicide truck bomber killed 14 people and wounded 87 in Arbil, capital of the relatively peaceful Kurdish region in the north.

The self-styled Islamic State in Iraq, an al Qaeda-led militant group, claimed responsibility for the attack which it said was in retaliation for the participation of the Kurdish Peshmerga forces in Maliki's Baghdad security plan.

Near the city of Kirkuk, three Iraqi journalists and their driver were dragged from their car, tortured and shot dead.

An explosion, apparently caused by a mortar bomb, rattled windows at the building in Baghdad's fortified Green Zone where Cheney and reporters traveling with him were working.

"His business was not disrupted," said Anne McBride, a Cheney spokeswoman. "He was not moved."

Mortar attacks on the Green Zone are frequent.

U.S. President George W. Bush is under pressure to show progress in the four-year war, in which more than 3,300 U.S. soldiers and tens of thousands of Iraqis have been killed.

During a visit to Baghdad last month, Defense Secretary Robert Gates said progress on a package of laws that include a bill dividing up Iraq's oil wealth would figure in Washington's decision to maintain higher troop levels.

PRESSURE TO SCRAP RECESS

With U.S. troops dying daily, American officials have urged the Iraqi parliament to scrap a two-month summer recess.

In Washington for meetings with U.S. officials, Iraq's national security adviser said an agreement has been worked out with the Iraqi parliament to reduce their planned vacation.

"We have managed to convince the Council of Representatives, the parliament, to cancel July vacation and even look into seriously considering canceling or reducing August vacation," Mowaffak al-Rubaie said in an interview on PBS' "The NewsHour with Jim Lehrer.

Iraqi lawmakers had bridled at U.S. pressure to shelve the holiday.

Cheney arrived in Baghdad on the day a USA Today/Gallup poll showed six in 10 Americans support setting a timetable for pulling out U.S. troops, even though a clear majority predict civil war in Iraq if U.S. forces withdraw next year.

Last week, Bush vetoed a war-spending bill because it called for a pullout of combat troops starting no later than October.

Gates said in Washington on Wednesday the United States could consider reducing troop levels in Iraq later this year.

Gates said a progress report in September from Gen. David Petraeus, overall commander in Iraq, and the U.S. ambassador would determine future troop levels.

"The question is whether the level of violence is such that the political process can go forward in Iraq. And that then sets the stage for us to begin drawing down our troops," Gates told a U.S. Senate subcommittee.

Many military strategists have said September is too soon to judge the effectiveness of the troop increase.

Cheney's visit to Iraq comes at a sensitive time. Leaders from the Sunni Arab minority have threatened to quit Maliki's government because they say Sunni interests are being ignored.

Washington says a Sunni role in government is needed to bring Sunnis firmly into the political process and tame the Sunni Arab insurgency.

Ethnic Kurds, staunch U.S. allies, have also threatened to block the oil bill in parliament.

The bill is another U.S. benchmark, along with a law to end a ban on former members of Saddam Hussein's Baath party from public office -- a plan that has met deep Shi'ite opposition. (Additional reporting by Shamal Aqrawi in Arbil, Dean Yates in Baghdad and Andrew Gray in Washington)

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