MANILA, Philippines - About 3,000 US Marines will not join annual war exercises in the Philippines starting this week because they are helping with relief work in quake- and tsunami-devastated Japan, officials said Sunday.

Philippine military spokesman Maj. Enrico Ileto said civic missions such as school construction will proceed as planned during the April 5-15 exercises, but some field exercises would be scaled back because of the US relief activities in northeastern Japan.

US Army Maj. Tage Rainsford said some Navy ships have also been deployed to Japan and would not join the Philippine exercises, which include joint training for possible natural disasters.

"They ended up in a real-world situation," Rainsford told The Associated Press.

About 6,000 Americans, along with 2,000 Filipino troops, were originally slated to join the exercises, called Balikatan or "shoulder-to-shoulder." The longtime military allies signed a 1951 Mutual Defense Treaty and later forged an agreement allowing US ship visits and American troops to join war maneuvers in the country.

About 500 American troops have been separately providing training, weapons and intelligence since 2002 to Filipino troops battling al-Qaida-linked militants in the country's south but they are barred from combat by the Philippine Constitution.