A U.S. soldier secures the scene of car bombing in central Baghdad, Iraq, 11 Feb 2008

Two car bombs have killed at least 19 people in Baghdad as U.S. Defense Secretary Robert Gates completed a two-day visit to Iraq.

The car bombs exploded almost simultaneously Monday in southern Baghdad, near a building where Sunni tribal chiefs opposed to al-Qaida were meeting. The tribesmen were among about 40 people wounded in the attack.

In another development, Iraqi officials say electricity has been cut in much of northern Iraq after two blasts hit the country's energy infrastructure.

An explosion this morning ruptured a natural gas pipeline that serves power stations in northern Iraq. Electricity supplies already had been disrupted Sunday by a truck bomb that damaged a power station in the northern city of Mosul.

U.S. Defense Secretary Gates said today in Baghdad that Iraq's security situation remains "fragile". He says he favors a "pause" in U.S. troop withdrawals from Iraq once initial pullouts are completed in July.

Gates was speaking after meeting the top U.S. commander in Iraq, General David Petraeus. Gates says a "brief period of consolidation and evaluation" to assess the impact of the initial pullouts "would make sense."

Most of the additional "surge" forces that President Bush ordered to Iraq last year are due to leave by July. U.S. officials must decide what to do after that.

Gates says General Petraeus' recommendation will be presented to the president next month, along with assessments by other senior officers and Gates himself. General Petraeus is to report to Congress in early April.

Also Monday, the U.S. military announced that an American soldier was killed by a roadside bomb Sunday in Iraq's Diyala province.

Some information for this report was provided by AFP and Reuters.