The Philippines has reached a "tentative understanding" with the United States for the return of Clark air base to Manila's control in September, Foreign Secretary Raul Manglapus said Monday.

The two countries had made tentative arrangements for the turnover to Philippine control of four smaller U.S. military bases in the country, Manglapus said.They are negotiating a new agreement to govern the use of Clark, Subic naval base and the four smaller bases north of Manila. The current U.S. lease on the facilities expires in September.

"There is a tentative understanding that we will take over Clark," Manglapus told reporters after briefing President Corazon Aquino on the results of last week's fourth round of talks between the two negotiating panels.

"We will take over Clark by Sept. 17 of this year," he said.

Clark and Subic are Washington's biggest military bases overseas. Clark is the headquarters of the 13th U.S. Air Force and Subic is a major repair yard and resupply base.