As expected, US President Barack Obama visited the border between the Republic of Korea and the Democratic People's Republic of Korea on Sunday. His visit came at a sensitive time and added further uncertainties to US-DPRK relations and international efforts to denuclearize the Korean Peninsula.

Arriving on the eve of the second Nuclear Security Summit, which is being hosted by the ROK, Obama went straight to meet troops at a US base on the edge of the Demilitarized Zone.

Created in 1953 after the Korean War ceasefire, the DMZ is a 4-kilometer-wide, 248-kilometer-long legacy of the Cold War that provides a buffer between the DPRK and the ROK; about 2 million combat forces are stationed on both side of the world's most heavily militarized zone.

Then on Monday, Obama issued a stern warning to the DPRK that its alleged pursuit of nuclear weapons undermines regional security.

No doubt Obama's DMZ visit and warning pleased the ROK and the 20,000 American troops still deployed there, but it was also calculated to play with voters back home. Unfortunately it cast yet another shadow on the already strained US-DPRK relations. Pyongyang could easily interpret such provocations as a threat.

The past few weeks had already seen some push and shove by the two countries. Pyongyang announced on March 16 that it would send a satellite into orbit on the back of a long-range rocket next month. Washington immediately condemned the proposed launch as a violation of the DPRK's promise to halt long-range missile launches, nuclear tests and uranium enrichment. Obama said the planned launch jeopardizes a deal for the United States to resume stalled food aid to the DRPK and may result in the tightening of harsh economic sanctions on the country.

The deal to resume US food aid, agreed between the two countries earlier this month, had been widely perceived as a positive development that could contribute to international efforts aimed at denuclearization of the peninsula. In exchange, for the food aid the DPRK agreed to suspend its nuclear tests, long-range missile launches and uranium enrichment activity at Nyongbyon, and to allow the International Atomic Energy Agency to monitor the moratorium on uranium enrichment.

Regrettably, since Pyongyang made public its rocket launch plan, the recent positive momentum toward reconciliation between Washington and Pyongyang has been disrupted. Following the threat to hold its promised food aid, the US made yet another gesture signaling tension in its relations with the DPRK. It announced on March 21 that it has suspended efforts to recover the remains of American war dead in the DPRK. The operation was only resumed last October after being stalled for six years.

It is against the backdrop of these newly emerged frictions that Obama stepped onto one of the world's most sensitive strips of land. It is difficult to predict to what extent Pyongyang will view this as provocation and what it will do in response. But it certainly makes it more difficult for the international community to persuade Pyongyang to drop its rocket launch plan now.

The current tension between Washington and Pyongyang has its root cause in the long-term enmity and deep political distrust between the two countries. Both should understand they have a responsibility to solve the Korean Peninsula issue in peace. Both sides should exercise restraint and always bear in mind the larger picture of regional stability.

Some have speculated that Obama's gestures could signal the DPRK nuclear issue will feature in the nuclear summit. Should this be so, it could distract international attention from nuclear materials security and nuclear facilities safety, issues that concern the global village as a whole. The DPRK nuclear issue should be reserved for its proper forum, the Six-Party Talks.

The Seoul summit should be a platform to unite governments and international organizations on endeavors such as ensuring safety of nuclear facilities and preventing nuclear terrorism. It should not be turned into a place where seeds of discord can be sown among members of the international community over complicated regional issues like the Korean Peninsula.

The author is a writer with China Daily. E-mail: wanghui@chinadaily.com.cn