North Korea has insisted on one-on-one meetings with the United States, hoping to win security guarantees and economic aid in exchange for giving up its nuclear programs. Washington considers Pyongyang's nuclear ambitions a regional threat and says any talks on the crisis should include China, Japan, South Korea and possibly Russia.
"Various forms of pressure on North Korea — I wouldn't call them sanctions but rather diplomatic pressure — would get the North to change its mind," said South Korean Unification Minister Jeong Se-hyun in an interview with Seoul's CBS radio (which is not affiliated with CBS News or CBSNews.com).
Jeong said talks including Japan and South Korea are "the North's only option" and that Pyongyang "is expected to change its attitude in one or two months."
His comments echoed those of a senior Japanese official. Japanese Deputy Cabinet Secretary Shinzo Abe said Sunday that continued pressure could bring a "dramatic turn" in North Korea's policies.
In recent weeks, the United States and its regional allies, most notably Japan and Australia, have tried to crack down on the North Korean trade in illicit drugs, weapons and counterfeit money — believed to be key sources of hard currency for Pyongyang.
Japanese authorities have beefed up inspections of North Korean ships long suspected of smuggling missile parts and narcotics between the two countries. In the past few days, they have detained one cargo ship and blocked another from docking for safety violations.
In April, Australian authorities raided a North Korean-owned ship and charged its crew with aiding and abetting the trafficking of heroin.
North Korea said Monday the developments were all part of a U.S. move to lay "an international siege" to North Korea.
Pyongyang's main state-run newspaper Rodong Sinmun accused Japan of "taking advantage of the U.S. imperialists' moves for 'economic sanctions,' 'sea blockade' and 'preemptive attack' over the (North)'s nuclear issue."
Also Monday, South Korea's JoongAng Ilbo newspaper, citing unnamed intelligence sources, said Iranian cargo planes traveled to North Korea six times since April, flying through airspace over China and Central Asia and carried back what appeared to be missile parts from Pyongyang.
Seven months ago, a shipment of North Korean Scud missiles bound for Yemen was briefly stopped in the Arabian Sea as a U.S. warning against the North's role in missile proliferation. JoongAng said Pyongyang now appears to be using aircraft instead of ships to export its missiles.
In Vienna, the head of the U.N. nuclear watchdog agency, Mohamed ElBaradei, said he could not be sure North Korea was not diverting "nuclear material for weapons or other explosive devices." Pyongyang expelled experts and monitors from the International Atomic Energy Agency late last year.
Foreign ministers of the 10-member Association of Southeast Asian Nations meeting in Phnom Penh, Cambodia's capital, planned to urge North Korea to rejoin the Nuclear Non-Proliferation Treaty, according to a draft joint communique to be issued Tuesday.
Tensions in the region have been mounting since October, when U.S. officials said North Korea admitted having a covert nuclear program. The United States and its allies cut off free oil shipments. North Korea retaliated by quitting the Nuclear Non-Proliferation Treaty and restarting its nuclear facilities.
North Korea has since announced publicly that it is seeking nuclear weapons and told American envoys that it already has "the bomb" and plans to reprocess fuel rods to create material that could be used to make more.
Pyongyang claims nuclear weapons are necessary both to counter the new, U.S. policy of preemptive strikes and to allow the cash-strapped North to whittle down its massive, costly conventional force.
Some observers believe the North is pressing for more aid.