South Korea Defense Minister Cho Young-kil has put the military on heighten alert as a precaution against what he called "possible provocative action." The alert comes amid reports that North Korea may be moving ahead with reprocessing its spent nuclear fuel rods.

In a letter in the Defense Ministry newspaper Thursday, Mr. Cho informed top military officers there is growing probability North Korea may launch various provocations to enhance its bargaining position in the nuclear dispute.

Since the United States accused North Korea of violating non-proliferation accords by having a secret nuclear weapons program in October, North Korea has taken a number of steps deemed provocative by the international community. Pyongyang has conducted missile tests, withdrawn from the nuclear Non-Proliferation Treaty, expelled international nuclear inspectors and reopened its main Yongbyon nuclear facility, which it had closed under a 1994 agreement with the United States.

Defense Minister Cho's warning comes amid reports of suspicious new activity Yongbyon.

A South Korean official on Thursday said the United States has given Seoul evidence that Pyongyang might be reprocessing spent nuclear fuel rods there. The official, who did not want to be named, said a spy satellite photograph shows smoke coming from the Yongbyon facility - a possible indication that North Korea has started reprocessing its eight-thousand spent fuel rods. That would be a key step toward producing nuclear weapons.

However, spokesmen at the White House and at South Korea's Unification Ministry say there is no conclusive evidence yet. They suggested Pyongyang may be bluffing to enhance its leverage in any future talks involving its nuclear weapons program.

North Korea met with U.S. and Chinese diplomats in Beijing last month - the highest-level contact in six months. U.S. officials say North Korea claimed to have nuclear weapons at that meeting. Experts and intelligence reports say it is possible that North Korea could have two nuclear bombs already and could produce more within months from the Yongbyon facility.

North Korea is demanding U.S. diplomatic recognition, formal security guarantees and massive economic aid in exchange for giving up its nuclear programs. The United States says that it is tantamount to blackmail - since North Korea is in violation of previous commitments to be nuclear free and has gotten fuel and other aid.

The United States plans to hold talks in the coming weeks with South Korea and Japanese leaders to discuss next steps regarding North Korea's nuclear activities.