South Korea, the U.S. and China are stepping up their diplomatic efforts this week to prevent North Korea from proceeding with a third nuclear test.

Satellite images of the North’s test site in the northeastern town of Punggye showed work under way last week. A Korean expert told reporters on Wednesday that Pyongyang appears to have finished its preparations.

The U.S. government said Thursday it has not detected any clear signs of an imminent atomic test “other than the rumors.” Seoul and Beijing made similar comments.

On Wednesday, South Korea’s top nuclear envoy Lim Sung-nam met with his Chinese counterpart Wu Dawei in Beijing.

“The two officials shared a consensus that it is not desirable (for North Korea) to perform a nuclear test again,” a senior government official told reporters, requesting anonymity due to the sensitivity of the matter.

North Korea tested its atomic devices on the heels of similar failures of rocket launches in 2006 and 2009.

Lim’s visit coincides with a trip by U.S. Secretary of State Hillary Clinton to the Chinese capital. She raised North Korea, Iran and other issues to President Hu Jintao on Thursday.

Washington and Beijing should “work together to make it clear to North Korea that strength and security will come from prioritizing the needs of its people, not further provocation,” Clinton said in her opening remarks to the two-day U.S.-China Strategic and Economic Dialogue.

China, the reclusive North’s sole ally and prime donor, has also issued veiled warnings against a potential atomic test although it largely eschews greater pressure and stronger sanctions against its impoverished ally.

Clinton’s remarks come a day after a U.N. Security Council committee decided to add three North Korean state firms to its blacklist, freezing assets and banning international trade.

The North’s failed rocket launch on April 13 triggered international condemnation, with the 15-member Council branding it a masqueraded long-range ballistic missile test. Pyongyang insists it intended to put a satellite into orbit for scientific purposes.

Embracing the strengthened sanctions, the five permanent council members urged North Korea to desist from any additional provocative acts.

“We call on (North Korea) to refrain from further actions which may cause grave security concerns in the region, including any nuclear tests,” said a joint statement by the United States, France, Russia, China and Britain released at a nuclear meeting in Vienna.

Meanwhile, North Korean state media said Friday its leader Kim Jong-un has inspected an air force unit in the latest in a string of his visits to frontline bases. Kim orchestrates the autocratic state’s 1.2 million-strong military as the supreme commander.

Tensions flared up two weeks ago when the repressive regime threatened to take “special actions” that could turn Seoul to ashes in minutes in retaliation for perceived insults during Pyongyang’s commemoration of the centenary of the birth of founding father, Kim Il-sung. 

By Shin Hyon-hee (heeshin@heraldcorp.com)