SEOUL (Reuters) - Chinese fishing vessels have moved out of waters near a disputed sea border between the two Koreas, a South Korean military official said on Wednesday, possibly signaling a North Korean short-range missile test is imminent.

North Korean leader Kim Jong-il (2nd R) visits the Hungnam fertilizer complex at the undisclosed place in North Korea, in this undated picture released by North Korea's official news agency KCNA February 7, 2009. REUTERS/KCNA

In another move that could stoke tensions, U.S. and South Korean news reports said the North has made further preparations to test its longest-range Taepodong-2 missile, with a launch possible in about a month.

North Korea usually orders its vessels to stay out of Yellow Sea waters off its west coast when it conducts short-range missile tests. China is the closest thing the North can claim as a major ally and is the impoverished state’s biggest benefactor.

“The (Chinese) fishing boats have disappeared, but no other unusual moves have yet been detected,” said an official with South Korea’s Joint Chiefs of Staff who asked not to be named.

During its last test launch of short-range missiles in that area in October 2008, the North issued a no-sail order to its ships a few days before firing off missiles, South Korean government officials have said.

North Korean short-range missiles have a range of about 100-150 km (60-95 miles), which means they can hit all of the Seoul area and many U.S. military bases in South Korea.

Experts say the North may have hundreds of short-range missiles, and that the missiles have a proven capability due to recent successful tests.

CNN reported on its website (edition.cnn.com/) that North Korea also appeared to have positioned telemetry equipment at an east coast missile base it used when it last launched its Taepodong-2 missile in 2006.

The missile, which has never successfully flown but is designed to hit U.S. territory, fizzled seconds after it was fired in that test.

There was no evidence of a Taepodong-2 being moved to a launch pad, the U.S. official was quoted as saying.

“Vehicles carrying equipment needed for missile launch were moving toward the (east cost) Musudan-ri base,” Yonhap news agency quoted a South Korean government source as saying.

The source said that if the North continued at its current pace, it could launch a Taepodong-2 in a month. South Korean officials were not immediately available for comment.

Impoverished North Korea, angry at the hardline policies of the South’s government, in recent weeks has stepped up tension by threatening to reduce its wealthy southern neighbor to ashes.

PRESSURE BUILDS

Analysts said the steps were aimed at putting pressure on the South and at attracting the notice of new U.S. President Barack Obama, who is sending Secretary of State Hillary Clinton to the region next week to discuss regional security concerns.

“We are hopeful that some of the behavior that we have seen coming from North Korea in the last few weeks is not a precursor of any action that would up the ante or threaten the stability and peace and security of the neighbors in the region,” Clinton told reporters in Washington on Tuesday.

The U.S. military stepped up its monitoring of North Korea this week amid concerns of possible missile launches, a U.S. military official said.

The foreign ministers of South Korea and Japan said after meeting in Seoul that North Korea should stop its provocations.

Leader Kim Jong-il has named senior military official Kim Yong-chun as the new defense chief, the North’s state media said, replacing a close confidant with another to set him up as one of the unquestioned leader’s more powerful aides.

Kim Jong-il, 66, who is suspected of suffering a stroke in August, has no challengers to his leadership, analysts said, but the North has rearranged ministerial posts in the past few months -- changing the alignment of the distant trailing pack of officials who might eventually succeed him.