BAGHDAD, Sept 10 (Reuters) - Iraq's Shi'ite Prime Minister Nuri al-Maliki is expected to address parliament on Monday hours before American officials deliver a vital progress report on Iraq to the U.S. Congress.

An official in Maliki's office and officials at parliament said the prime minister was expected to appear before lawmakers. The session opens at around midday (0800 GMT), although it was unclear precisely when Maliki would speak.

Maliki will likely defend his government's record in the face of blistering criticism from Iraqi and U.S. lawmakers. Some opposition Democratic legislators in the United States have called for him to be replaced.

Later on Monday in Washington, the U.S. military commander in Iraq, General David Petraeus, will give his assessment of President George W. Bush's decision to send an extra 30,000 troops to Iraq when he testifies before Congress.

A U.S. official who asked not to be identified said on Sunday that Petraeus and the U.S. ambassador to Iraq, Ryan Crocker, will argue that a major pullout of forces would hurt progress made since troop levels were increased to 168,000.

The assessment by Petraeus and Crocker is considered crucial to any decisions by Bush on force levels as he faces demands from Democrats and some senior Republicans for U.S. troops to start leaving Iraq.

Bush's top officials in Iraq are expected to highlight improved security but criticise Iraq's politicians for failing to pass laws seen as vital to healing sectarian divisions between warring majority Shi'ites and Sunni Arabs.

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