Washington is set to ratchet up diplomatic efforts to have other countries implement sanctions against Pyongyang based on a UN Security Council resolution as it prepares its own additional punitive measure to block North Korea’s financial accounts for illegal activities.

Robert Einhorn, US State Department special advisor for nonproliferation and arms control, will visit South Korea Sunday and then Japan for policy consultations to impose additional sanctions on North Korea.

The US point man on sanctions against the North and Iran plans to tour Southeast Asia and Europe as well as Northeast Asia in efforts to secure the effectiveness of international sanctions on North Korea.

But the US reportedly has no plans for stronger unilateral measures such as the one it took against companies trading with firms related to the Iranian nuclear programme.

The United States Thursday urged China to use its leverage on North Korea and faithfully implement international sanctions to persuade the reclusive communist state to stop provocations and abide by its denuclearization pledge.

“We would expect China to live up to its international obligations,” State Department spokesman Philip Crowley said. “But at the same time, we want to see China use its leverage with North Korea to encourage North Korea to move in a fundamentally different direction.”

Crowley spoke in response to China’s signing of a new economic cooperation agreement with North Korea earlier in the day even as Seoul, Washington and their allies step up efforts to sanction Pyongyang after the North’s torpedoing of a South Korean warship.

“I’m not familiar with the agreement or its terms,” Crowley said. “Clearly, China, as a neighbour of North Korea, has become an increasing factor in North Korea’s economy. That’s a matter for China and North Korea. However, China has responsibilities with respect to specific aspects of UN Security Council resolutions as they pertain to the areas of concern: our proliferation concern, our nuclear concerns in particular.”

China, North Korea’s staunchest communist ally and its primary source of food, fuel and other necessities, has taken the sting out of UN sanctions issued after North Korea’s nuclear and missile tests early last year.

China is believed to fear any instability across its border, which could lead to a massive inflow of refugees. It also enjoys a buffer zone, which would vanish with a unified Korea led by South Korea and its ally, the United States.

Crowley also called on Burma Thursday to abide by an arms embargo and other UN sanctions imposed on North Korea for its nuclear and missile test last year.

The remarks came as North Korean foreign minister Pak Ui-chun arrived in Yangon, Burma, earlier in the day for a four-day trip.

“We have concerns about the nature of the relationship between North Korea and Burma,” Crowley said. “We don’t see the transparency in that relationship that we’d like to see. North Korea is a serial proliferator. North Korea is engaged in significant illicit activity. Burma, like other countries around the world, has obligations, and we expect Burma to live up to those obligations.”

Arms sales are one of the major sources of revenue for North Korea, suspected of being behind nuclear and missile proliferation in Syria, Iran, Pakistan and several other countries.

Last June, a North Korean cargo ship, possibly on its way to Burma, returned home after being closely tracked by US navy vessels.

Israel said in May that the 35 tons of North Korean arms seized at the Bangkok airport in December were destined for the Hamas and Hezbollah militant groups via Syria.

Dennis Blair, then US director of national intelligence, has said the cargo was bound for the Middle East, without elaborating.