(Adds details) BAGHDAD, May 9 (Reuters) - U.S. Vice President Dick Cheney arrived in Baghdad on Wednesday on an unannounced visit, at a time when pressure from Washington is growing on the Iraqi government to meet political benchmarks aimed at healing sectarian divisions. John Roberts, the U.S. embassy information officer in Baghdad, said Cheney would meet with senior Iraqi officials. He gave no further details. Cheney is on a tour of the Middle East. U.S. President George W. Bush, who is sending 30,000 extra troops to Iraq for a security crackdown seen as a last ditch effort to stave off civil war, is under mounting pressure from Democrats to show concrete progress in the four-year-old war. During a visit to Baghdad last month, U.S. Defense Secretary Robert Gates said he hoped Iraq's parliament would not go into a summer recess without agreeing a package of laws that included a bill dividing up Iraq's oil wealth.
