SEOUL — South Korea President Lee Myung-bak on Monday cut trade to North Korea and vowed to seek U.N. Security Council action in response to the rogue nation’s March 26 torpedo attack on the patrol boat Cheonan.

He also promised any future “provocative” acts by North Korea will be dealt with immediately.

“From now on, the Republic of Korea will not tolerate any provocative act by the North and will maintain a principle of proactive deterrence,” Lee said in a nationally televised speech. “If our territorial waters, airspace or territory are militarily violated, we will immediately exercise our right of self-defense.”

He said the South has “always tolerated North Korea’s brutality, time and again. We did so because we have always had a genuine longing for peace on the Korean peninsula. But, now things are different. North Korea will pay a price corresponding to its provocative acts.”

But the president made no mention of any military response to the March 26 sinking of the Cheonan that killed 46 of the 104 South Korean sailors aboard.

Lee, along with South Korea’s ministers of unification, foreign affairs and defense, said South Korea will take the following steps in retaliation for the sinking of the Cheonan:• Ask the U.N. Security Council to take action against North Korea.• Stop all inter-Korean trade and exchange, with the exception of the Kaesong Industrial Complex, where some 1,000 South Koreans will continue to be allowed to commute north of the Demilitarized Zone to work with 42,000 North Koreans at 120 South Korean-owned plants.•Prohibit North Korean ships from passing through South Korean waters.•Resume “psychological warfare,” such as the broadcasting of anti-North Korean propaganda, and floating anti-Pyongyang leaflets by balloons across the Demilitarized Zone — actions that were stopped by agreement between the two countries in 2004. South Korean humanitarian aid to North Korea will still be allowed.•Stage a number of military naval and submarine exercises in the months ahead.

Pentagon spokesman Bryan Whitman said on Monday that the U.S. would join South Korea for an anti-submarine exercise and a maritime interdiction exercise in the near future.

“The overriding goal of [South Korea] is not military confrontation,” Lee said. “Our goal has always been the attainment of real peace and stability on the Korean peninsula. Our goal is to bring about prosperity for all Koreans.”

Asia experts Monday said the measures Lee announced were restrained and appropriate.

That is the “sensible” and “rational” approach to take, said longtime Seoul-based journalist Michael Breen, author of “The Koreans” and “Kim Jong Il: North Korea’s Dear Leader.”

“The farther you are away from the situation, the easier it is to be an armchair warrior and think, ‘Well, South Korea is behaving weakly,’” he said. “But, the North Koreans are far more prepared to risk everything than the South Koreans.”

U.S. Secretary of State Hillary Rodham Clinton, scheduled to visit South Korea on Wednesday, told reporters in Beijing that China and all of North Korea’s neighbors understand the “precarious situation the North Koreans have caused in the region” and want to contain it.

North Korea must get the message that, “We are not simply resuming business as usual,” she said.

A multinational team of investigators announced Thursday that evidence is “overwhelming” that a North Korean submarine fired a torpedo that ripped the Cheonan in half as the ship patrolled the Yellow Sea near the maritime border between the two Koreas.

North Korea has repeatedly denied involvement since the sinking. After Lee’s speech Monday, the official North Korean news agency quoted a commander as saying any speakers set up at the DMZ to blast propaganda to the North would be fired upon.

Breen said Monday’s speech marked the end of an era — South Korea’s decade-old “Sunshine Policy” of economic cooperation and openness toward North Korea which is now “officially dead.”

“The North Koreans now have badly bitten the hand that feeds them, and they’ve reminded a new generation ... what they’re really like,” he said.

Daniel Pinkston, a North Korea expert with the International Crisis Group, a multinational nonprofit organization, called the approach of the Lee administration “prudent and thoughtful.”

“[Lee] was very clear he wants to signal that these types of provocative actions cannot be tolerated,” Pinkston said.

“I am not a pacifist,” he added. “There are cases and times when force is justified and should be employed. But, in this case, I fail to see how military retaliation at this point would make South Korea better off.

“Sometimes you have to show some restraint … and be smart. Being tough is not always the best answer.”

Bruce Bechtol, an international relations professor at the Marine Corps Command and Staff College in Quantico, Va., said economic measures against the North would be more than symbolic.

“That’s where [the South] can really hurt them,” he said, pointing out that South Korea is responsible for roughly 30 percent of North Korea’s trade.

However, he said, the biggest thing South Korea could do would be shut down the Kaesong Industrial Complex, which accounts for about 65 percent of the South’s trade with the North.

“That [would be] a huge cut in money to the North Korean government if they do that,” Bechtol said.

Scott Snyder, director of the Center for U.S.-Korea Policy at the Asia Foundation, said it will be interesting to see how China acts when the matter is brought to the U.N. Security Council.

“There’s almost no doubt in my mind that there will be a new U.N. Security Council resolution, but China will try to water that down as much as possible,” he said.

Stars and Stripes reporters Ashley Rowland and Kevin Baron and The Associated Press contributed to this report.

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