The U.S. and South Korea are planning two major military exercises off the Korean Peninsula in a display of force intended to deter North Korean acts like the March torpedo attack on a South Korean warship.

President Barack Obama ordered his military commanders to coordinate closely with their South Korea counterparts "to ensure readiness and to deter future aggression" by North Korea, the White House said.

Pentagon spokesman Bryan Whitman told reporters on Monday the joint exercises will be conducted in the "near future." He said the operations will test the nations' ability to defeat submarines and to monitor and prevent illicit activities.

"We think that this is an area where, working with the Republic of Korea, we can hone some skills and increase capabilities," said Whitman.

The military exercises would be a decisive display of force after last week's finding by a team of international investigators that North Korea torpedoed a South Korean warship on March 26 that killed 46 South Korean sailors. It was South Korea's worst military disaster since the Korean War.

More than 28,000 U.S. troops are stationed in South Korea, an important regional ally. Previously, the Obama administration has been intentionally vague on how it might respond, reflecting U.S. reluctance to stoke tension unnecessarily.

U.S. Secretary of State Hillary Rodham Clinton -- in Beijing to win support from China, North Korea's top ally, for diplomatic action -- said Monday the Obama administration is striving to avoid a conflict on the Korean peninsula.

"We are working hard to avoid an escalation of belligerence and provocation," Clinton said. "This is a highly precarious situation that the North Koreans have caused in the region." The U.S. will work with other nations to make sure that North Korea feels the consequences of its actions and changes its behavior to avoid "the kind of escalation that would be very regrettable," she said.

In its statement Monday, the White House endorsed President Lee Myung-bak's demand that "North Korea immediately apologize and punish those responsible for the attack, and, most importantly, stop its belligerent and threatening behavior." Seoul can continue to count on the full backing of the United States, the White House said.

The South Korean president said that his nation would no longer tolerate the North's "brutality" and said the repressive communist regime would pay for the attack He also vowed to cut off all trade with the North and to take Pyongyang to the U.N. Security Council for punishment over the sinking of the warship Cheonan.

Obama, in response to North Korea's pattern of "provocation and defiance of international law," has ordered U.S. government agencies to review their policies toward Pyongyang.

The White House said Secretary of Defense Robert Gates remains in close contact with the South Korean defense minister and will meet with him next month in Singapore.

Whitman declined to say when the exercises will take place or whether they would require additional U.S. resources in the region.