MANILA — With a standoff between Philippine and Chinese ships under way in a disputed corner of the South China Sea, senior leaders from the United States and the Philippines have reaffirmed their longstanding commitment to mutual defense.

“We oppose the threat or use of force by any party to advance its claim,” Secretary of State Hillary Rodham Clinton said after the meeting Monday in Washington. “And we will remain in close contact with our ally, the Philippines.”

Mrs. Clinton and Defense Secretary Leon E. Panetta met with their Philippine counterparts, Foreign Secretary Albert del Rosario and Defense Secretary Voltaire Gazmin. They discussed broadening their military alliance as well as expanding economic and cultural ties, though no specific new initiatives were announced.

The meeting took place as the standoff in the South China Sea entered its fourth week. Since April 8, maritime vessels from China and the Philippines have been stationed at Scarborough Shoal, a disputed string of rock outcroppings about 200 kilometers, or 125 miles, west of Luzon Island in the northern Philippines. Both countries claim the area and have demanded that the other leave.