U.S. Ambassador to Iraq Ryan Crocker speaks during a press conference in Baghdad, 28 May 2007

The U.S. ambassador to Iraq says the situation there could become much worse if the United States pulls out of the country.

Ryan Crocker spoke to an American radio network, National Public Radio in an interview to be broadcast Wednesday.

He said in the case of a U.S. pullout it must be considered whether al-Qaida would assume power in Iraq, and what that would mean for security. He also said U.S. officials must consider how a total breakdown in security would impact Iraq's neighbors, and what Iran, Turkey and Arab states would do.

Crocker spoke as a suicide car bomber killed at least 15 people Tuesday at a market near the town of Fallujah.

The U.S. military says an American soldier was killed Tuesday when his patrol was attacked in southern Baghdad.

In other news, U.S. military officials played down a military report that says the Baghdad security operation is moving slower than expected. The officials said the report is not meant as a review of the effectiveness of the security operation, and that they expect to start seeing results in the coming months.

The report says the Baghdad security operation has been slowed by Iraqi forces unable to maintain security in cleared areas. It also says some Iraqi units lack sufficient manpower or have sectarian loyalties.

Some information for this report was provided by AFP.