(Updates with Bush comments, paragraphs 1, 5-6)

By Dean Yates

BAGHDAD, Sept 8 (Reuters) - Bombs killed 20 people in Iraq on Saturday, including 15 in Baghdad, police said, as U.S. President George W. Bush said his resolve to press on with the job of stabilizing Iraq was as strong as ever.

Police said a parked car exploded near a police station in Baghdad's Shi'ite area of Sadr City at dusk, when people were shopping. The blast killed 15 people and wounded 45, they said.

Another explosion at a market in the holy Shi'ite town of Kufa, possibly caused by a roadside bomb, killed five people and wounded eight, police said.

The bombs were a reminder of Iraq's security headaches despite a reduction in violence following Bush's decision early this year to send 30,000 additional troops to Iraq.

Bush, visiting wounded soldiers at Hickam Air Force Base in Hawaii as he headed back to Washington from an overseas trip, said he told them he was encouraged by what he saw during his unannounced trip to Iraq last Monday.

"There's no question there's still hard work to do. But my resolve is as strong as it has ever been," Bush told reporters.

Bush used his Saturday radio address to appeal for patience from opposition Democratic lawmakers demanding a timetable for a troop withdrawal.

The coming week could be a pivotal period in the unpopular war.

Starting on Monday, the U.S. commander in Iraq, Gen. David Petraeus, and Ambassador Ryan Crocker will give an assessment to the Democratic-led Congress on Iraq's security and political progress under Bush's troop "surge."

Bush's administration has to give its own report to Congress by next Saturday.

"I urge the members of Congress to listen to these two well-respected professionals -- before jumping to any conclusions," Bush said, referring to his top officials in Iraq.

The testimony by Petraeus and Crocker will be vital to any decision Bush takes on troop numbers in the face of demands from Democrats and some senior Republicans for U.S. forces to start leaving Iraq.

TELEVISED ADDRESS PLANNED

Fresh from his visit to Iraq, where he raised the possibility of cutting troop levels, Bush said he would make his own case in a televised address after Petraeus and Crocker deliver their reports. CNN said Bush would speak on Thursday.

"I will discuss the changes our strategy has brought to Iraq. I will lay out a vision for future involvement in Iraq -- one that I believe the American people and their elected leaders of both parties can support," Bush said.

Petraeus and Crocker are expected to highlight improved security but criticize Iraq's politicians for failing to pass laws seen as vital to healing sectarian divisions between warring majority Shi'ites and Sunni Arabs.

Petraeus conceded in a letter to troops on Friday that the Shi'ite-dominated government's record on political reforms had been disappointing.

The Bush administration boosted troop levels -- now at 168,000 -- as part of a plan to improve security and give Iraqi politicians time to start bridging the sectarian divide.

Iraqi politicians said Prime Minister Nuri al-Maliki could address parliament in the coming week. The agenda was unclear.

A small Sunni Arab party returned to Iraqi's parliament on Saturday after a boycott of more than two months.

The Iraqi National Dialogue Front, which has 11 seats in the 275-member legislature, suspended its participation in June, partly over the firing at the time of the speaker, a Sunni Arab from a larger Sunni Arab bloc. (Additional reporting by Ross Colvin and Waleed Ibrahim in Baghdad, Matt Spetalnick in Sydney and Caren Bohan in Hawaii)

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