By BURT HERMAN
The Associated Press
Wednesday, October 18, 2006; 11:02 PM

SEOUL, South Korea -- This would be the scenario: North Korean ships suspected of carrying weapons would be halted at sea by a U.S.-allied naval force, with commandos swooping in from helicopters to search the vessel from bow to stern.

Envisioned under the U.S. Proliferation Security Initiative, the prospect of such a search is receiving new impetus since North Korea's nuclear test _ and Washington is pressuring South Korea to sign on.

The Bush administration has been trying for years to get more nations to join its anti-proliferation initiative, aimed at stopping countries like North Korea from selling nuclear weaponry and missiles.

The U.S. ambassador to South Korea, Alexander Vershbow, said Wednesday that Secretary of State Condoleezza Rice would ask South Korea when she visits Seoul on Thursday "to join with others to expand cooperation" in the effort.

So far, South Korea has been noncommittal.

South Korean Vice Foreign Minister Lee Kyu-hyung said Wednesday that the Proliferation Security Initiative and the U.N. resolution sanctioning the North for its nuclear test were "separate issues." He added that Seoul was "considering adjusting our role at an appropriate and necessary level, that is in line with contents of the U.N. resolution."

However, a report by South's Yonhap news agency Thursday suggested that Seoul could be rethinking its plans and may move to inspect North Korean ships that stop at South Korean ports. Officials didn't immediately confirm the report.

The Proliferation Security Initiative was announced in 2003 in the wake of the Sept. 11 attacks as an attempt to work with other navies and air forces to monitor and potentially intercept ships or aircraft suspected of ferrying illicit materials to rogue nations or to terrorists.

It started with 10 partners, including France, Germany, Japan and Britain, and Defense Secretary Donald H. Rumsfeld said this month it has grown to about 60 participating countries. The Pentagon and State Department have been trying to develop it into a stronger tool.

Rumsfeld conceded the initiative "has holes in it," including the absence of an internationally accepted legal basis for confiscating some materials on the high seas.

South Korean participation is deemed critical because North Korean ships now pass through the South's territorial waters under agreements between the two sides. The Proliferation Security Initiative in itself isn't empowered to search ships in international waters because of laws guaranteeing free passage.

Some allege North Korean ships that passed through the South's waters may have been involved in preparations for the North's Oct. 9 nuclear test.

Song Young-sun, an opposition legislator and defense expert, has raised questions about North Korean ships transiting South Korean waters that are officially declared empty _ which would seem a waste of resources by energy-starved Pyongyang.

Of 136 ships from last year through September that passed through the Jeju Strait separating the southern coast of the peninsula from South Korea's Jeju Island, Song said 24 of 28 empty ships went from the North's western port of Nampo to the eastern port of Kimchaek.

Kimchaek is about 40 miles south of where the North is believed to have conducted its nuclear test; Nampo is about 70 miles south of the North's main nuclear facility at Yongbyon.

Traveling by land between those two sites would be difficult, and Song noted the North's rail lines are decrepit. The country also suffered floods in July that knocked out roads and bridges.

Song also expressed concern that North Korean ships could be masking transit of submarines _ or even that North Korean suicide bombers hiding aboard could speedily cross the narrow strait to the South Korean city of Busan, a key naval headquarters and the country's only deep military port that can service warships.

Song noted the South Korean military had yet to stop and search a single North Korean ship, even though it has the right to do so under a 2005 maritime agreement between the two Koreas.

The South Korean Defense Ministry argued there was no reason to perform such searches yet, although it acknowledged it had the right to do so if it had suspicions or intelligence on possible weapons shipments.

Seoul is coming under more pressure than ever to change that hands-off stance, with the United States calling on South Korea to commit to the Proliferation Security Initiative.

"This is the time for South Korea to become a member," said Kim Tae-woo, a North Korea expert at the South's Korean Institute for Defense Analyses, who has called on Seoul to take a tougher line with the North.

Seoul knows the anti-proliferation initiative infuriates the North _ which lashed out at South Korea in February for simply sending observers to exercises.

The worry here is that things could quickly spiral out of control, with the two Koreas also at odds over how their sea border is defined.

Warships from the North and South have clashed before. Battles as recently as 1999 and 2002 left several sailors dead.

Still, Kim argued, it's time for Seoul to get in step with the international community and stop granting the North concessions without getting anything in return under its reconciliation policy.

"This is a real time for sticks rather than carrots," he said.