By Li Hongmei

The Democratic People's Republic of Korea (DPRK) could perform a fourth underground nuclear weapons test at Punggye-ri, the site of its previous test. Pyongyang appeared to be making preparations for the test, according to a South Korean government source speaking to the country's Joong Ang Daily newpaper.

This comes on the heels of the South's defense ministry reports that Pyongyang could perform a mid-range missile test-launch by Wednesday - also the deadline it has given to foreign diplomats to evacuate, as their safety would reportedly no longer be guaranteed by the government.

A top US military officer said on Sunday the Pentagon had bolstered its missile defenses and taken other steps because he "can't take the chance" that the Democratic People's Republic of Korea (DPRK) won't soon engage in some military action.

Heightened tensions with the DPRK led the United States to postpone congressional testimony by the chief US commander in South Korea and delay an intercontinental ballistic missile test from a West Coast base.

The DPRK, after weeks of war threats and other efforts to punish South Korea and the US for joint military drills, has told other nations that it will be unable to guarantee diplomats' safety in the capital of Pyongyang beginning April 10 (Wednesday).

US Gen Martin Dempsey, the Joint Chiefs of Staff chairman who just wrapped up a visit to Afghanistan, was asked whether he foresees Pyongyang taking military action soon.

"No, but I can't take the chance that it won't," he said, explaining why the Pentagon has strengthened missile defenses and made other decisions to combat the potential threat.

Dempsey said the US has been preparing for further provocations or action, "considering the risk that they may choose to do something" on one of two nationally important anniversaries in April - the birth of North Korean founder Kim Il Sung and the creation of the Korean people's army.

US Gen James Thurman, the commander of the 28,000 American troops in South Korea, will stay in Seoul as "a prudent measure" rather than travel to Washington to appear this coming week before congressional committees, Army Col. Amy Hannah said in an email on Sunday to the AP.

Thurman has asked the Senate Armed Services Committee, the House Armed Services Committee, and the House Appropriations subcommittee on defense to excuse his absence until he can testify at a later date.

Dempsey said he had consulted with Thurman about the rising tensions on the Korean peninsula.

Dempsey said both Thurman and South Korea's joint chiefs of staff chairman, Gen Jung Seung-jo, decided it would be best for them to remain in Seoul rather than come to Washington. The Korean general had planned to meet with Dempsey, the US joint chiefs of staff chairman, in mid-April for regular talks.

Dempsey said that instead of meeting in person with Thurman and Jung in Washington, they will consult together by video-teleconference.

The Pentagon has postponed an intercontinental ballistic missile test that was set for the coming week at Vandenberg Air Force Base in California, according to a senior defense official.

The official said US defense secretary Chuck Hagel decided to put off the long-planned Minuteman 3 test until April because of concerns the launch could be misinterpreted and exacerbate the Korean crisis. Hagel made the decision on Friday, the official said.

On the other hand, the DPRK's military said this past week that it was authorized to attack the US using "smaller, lighter and diversified" nuclear weapons. The DPRK also conducted a nuclear test in February and in December launched a long-range rocket that could potentially hit the continental US.

The US has moved two of the navy's missile-defense ships closer to the Korean peninsula, and a land-based system is being deployed to the Pacific territory of Guam later this month. The Pentagon last month announced longer-term plans to strengthen its US-based missile defenses.

A South Korean national security official said on Sunday that Pyongyang may be setting the stage for a missile test or another provocative act.

Citing the DPRK's suggestion that diplomats leave the country, South Korean President Park Geun-hye's national security director said Pyongyang  may be planning a missile launch or another provocation around Wednesday, according to presidential spokeswoman Kim Haing.