Defense Secretary Robert Gates scrapped plans to go on a four-nation tour of Latin America this week and will instead stay home to attend meetings on Iraq, the Pentagon announced Sunday.

The meetings are related to a progress report on Iraq that is due to be delivered to Congress by July 15.

Congress mandated the preliminary report and required it to be followed by another one in September. The report's findings could add to the pressure to end the war or change strategies.

It is due out as a growing number of moderate Republicans, including Sen. Richard Lugar of Indiana, a member of the Foreign Relations Committee, voice concerns.

Lugar told a cable news show on Sunday that the United States should start reducing its military presence in Iraq. But he added that careful consideration must be given over how to do that.

"We really have to be thoughtful as to physically how our troops could get out of Iraq," Lugar said.

The Senate is expected to start debate this week on a bill authorizing military spending in Iraq for the fiscal year starting in October.

Gates' trip was to have included meetings with defense and political leaders in El Salvador, Columbia, Peru and Chile. He will travel to the region at an unspecified later date, the Pentagon said in a statement.

Gates is sticking with plans to attend a change of command ceremony in Tampa, Fla., on Monday as previously intended.

Navy Adm. Eric Olson will take over as head of the military's Special Operations Command, from the current chief, Army Gen. Bryan Brown. Olson is the first Navy officer to run the command.