The United States is pressuring China's new President Xi Jinping to crack down on the regime in North Korea or face an increased US military presence in the region, The New York Times reported late Friday.

Citing unnamed administration officials, the newspaper said the recent US exchanges with China included a phone call from President Barack Obama to Xi.

US officials briefed the Chinese in detail about US plans to upgrade missile defenses and other steps to deter the threats made by North Korea's young leader, Kim Jong-un, the report said.

China has not protested publicly or privately as the United States has deployed ships and warplanes to the Korean Peninsula, the paper noted.

That silence attests to both Beijing's mounting frustration with North Korea and the recognition that its reflexive support for Pyongyang could strain its ties with Washington, the report said.

"The timing of this is important," The Times quoted US national security adviser Tom Donilon as saying in an interview. "It will be an important early exercise between the United States and China, early in the term of Xi Jinping and early in the second term of President Obama."

According to the paper, in the coming weeks, the White House will send a stream of senior officials to China to press its case, starting with Secretary of State John Kerry, who will travel to Beijing next Saturday.

In the short run, the report said, the administration wants the Chinese to be rigorous in customs inspections to interdict the flow of banned goods to North Korea.

But in the long run, it wants China to persuade Kim to cease his provocations and agree to negotiations on giving up his nuclear program, The Times said.

N. Korea maintains access ban to industrial zone
Seoul (AFP) April 6, 2013 - North Korea refused on Saturday to lift a ban on South Koreans accessing their companies in a joint industrial zone on the North side of the border.

Entry to the Seoul-funded Kaesong complex has been barred since Wednesday, as inter-Korean tensions have risen to their highest level for years.

A few trucks with supplies and raw materials had optimistically turned up early at the border crossing to Kaesong, but turned back after being told the North Korean side was still not allowing any people or vehicles to cross.

South Korean managers have warned that the blocking of raw materials and personnel movement could force them to shut their Kaesong operations in a matter of days.

Pyongyang has allowed those South Koreans still inside Kaesong to leave, and 92 crossed back to the South on Saturday, leaving 516 South Koreans in the complex, the South's Unification Ministry said.

Korean Unification Minister Ryoo Kihl-Jae said Friday that Seoul would consider pulling its citizens out of Kaesong if their situation becomes untenable.

Pyongyang has already threatened to pull out its 53,000 workers hired by 123 South Korean companies there and shut the whole complex down.

Kaesong, which lies 10 kilometres (six miles) inside the North, was established in 2004 and is a crucial hard currency source for North Korea.

EU diplomats in Pyongyang in 'constant contact': sources
Brussels (AFP) April 05, 2013 - The diplomats of the seven EU countries with embassies in North Korea are in close and constant contact after Pyongyang's warning they may have to leave, diplomatic sources said Friday.

The sources said the embassies of EU member states in Pyongyang were "in permanent contact and are assessing the situation" after North Korea said it could not guarantee their safety after April 10.

EU members Britain, Germany, Bulgaria, Czech Republic, Poland, Romania and Sweden have diplomatic representation in isolated North Korea which has ratcheted up the tension with threats to launch nuclear attacks on the United States.

Bulgaria's foreign ministry said the chief of all EU missions in Pyongyang had agreed to meet Saturday to discuss a common position.

The sources said representatives of all 27 EU states would meet Monday in Brussels to review.

The EU does not have a separate presence in Pyongyang but "is following developments through its delegations in Seoul and Beijing," one source said.

"We are also in close coordination with our international partners, especially South Korea, China, Japan and the United States," the source added.

Russian Foreign Minister Sergei Lavrov said Moscow, which has relatively close ties with Pyongyang, was consulting with China over the warning, as well as the United States.

In London, the Foreign Office said Pyongyang had warned that from April 10, "the North Korean government would be unable to guarantee the safety of embassies and international organisations in the country in the event of conflict."

"Our understanding is that the North Koreans were asking whether embassies are intending to leave, rather than advising them to leave," a Foreign Office spokeswoman said.