BAGHDAD, Iraq (Reuters):

A bomb killed 15 people and wounded 55 in the second atttack in as many months on Baghdad's much-loved Friday pet fair; the latest in a string of bombings at the city's markets that have killed over 150 this week.

One of President George W. Bush's key critics in Congress - new House of Representatives speaker Nancy Pelosi - met Iraqi Prime Minister Nuri al-Maliki and other officials. An opponent of Bush's plan to send 20,000 more troops, Pelosi said she also came to applaud the courage of Americans fighting in Iraq.

A police source said witnesses believed yesterday's market bomb was planted in a cardboard box that the bomber had punched with air holes to pass it off as containing birds. Parrots, canaries and more exotic pets are prime attractions at the Ghazil market.

Two months ago, three people were killed at the Friday fair, which attracts weekend sightseers in the beleaguered city.

Blood stained the ground and small birds chirped in battered cages around the small square in front of an ancient Sunni mosque. Tattered black Shi'ite prayer flags hung in the clear, still air. The population of the busy area is religiously mixed.

Phased withdrawal of US

Newly empowered by victory at November's U.S. Congressional elections, Bush's Democrat opponents are pushing for a phased withdrawal of U.S. troops and have fiercely opposed Bush's plans to send more troops to back a big security crackdown in Baghdad.

With other U.S. lawmakers, Pelosi met U.S. and Iraqi officials including Maliki and said she came out of the meeting, "with a greater understanding of each other's point of view".

Pelosi, who has accused Bush of playing politics with U.S. soldiers' lives, said she was also visiting Iraq to thank the troops and "applaud their patriotism, the sacrifice they're willing to make and the courage they're demonstrating".

With her in Baghdad was another fierce critic of the war, Representative John Murtha, a fellow Democrat and former marine.