BEIJING (Reuters) - North Korea is becoming a direct threat to the United States and could develop an inter-continental ballistic missile within five years, Secretary of Defense Robert Gates said on Tuesday.

North Koreans attend a mass rally on the Kim Il Sung square in Pyongyang January 3, 2011. REUTERS/Kyodo

The latest U.S. assessment of the missile threat -- offered by Gates in the capital of North Korea’s only ally, China -- appeared to confirm projections the American intelligence community first issued in 2001.

Gates praised Chinese efforts to reduce tension on the Korean peninsula but also stressed the urgency to rein-in the reclusive state, which has twice tested nuclear devices.

China is Pyongyang’s top diplomatic and economic backer, and Gates said North Korea would likely come up in talks between Chinese President Hu Jintao and President Barack Obama in Washington next week.

“With the North Koreans’ continuing development of nuclear weapons and their development of inter-continental ballistic missiles, North Korea is becoming a direct threat to the United States,” Gates told reporters after talks with Hu.

Gates said he did not believe North Korea was an immediate threat, but added that it was also not a “five-year threat.”

“I think that North Korea will have developed an inter- continental ballistic missile within that time -- not that they will have huge numbers or anything like that,” Gates said. “But ... I believe they will have a very limited capability.”

A senior U.S. official in Washington told Reuters the United States “will have to respond to this threat.”

“We are open to responding to it by diplomacy but if the North Koreans don’t come to the table and indicate their willingness to address it, then we will do what is necessary to defend the country,” said the official, who spoke on condition of anonymity and declined to elaborate on U.S. plans.

Analysts said the threat Gates raised was first identified in the 2001 U.S. National Intelligence Estimate, which projected that during the next 15 years the United States would “most likely” face ICBM threats from North Korea and Iran.

“Those who follow North Korea know that this has been a threat long in the works,” said Bruce Klingner, a Korea expert at the Heritage Foundation in Washington.

But he said Gates can be assumed to be working from current intelligence, which could reflect that the 2009 long-range “Taepodong 2 test launch, which though was seen as a failure, actually doubled the effective range of that missile.”

Nikolas Gvosdev of the U.S. Naval War College saw in Gates’ remarks a signal to China “that it will no longer be able to wink at North Korean antics if the U.S., Japan and South Korea now see the regime as a fundamental threat.”

North Korea’s arsenal already includes intermediate-range missiles that can hit targets at up to 3,000 km (1,860 miles) away, the Yonhap news agency quoted a South Korean official as saying last year. Those missiles could hit all of Japan and put U.S. military bases in Guam at risk.

WORST-CASE SCENARIO

North Korea has been seeking to develop long-range missiles for over a decade. Tests of its Taepodong-2, with an estimated range of 6,700 km (4,160 miles), suggested, however, it was still a long way off from producing the complete weapon.

In a 2006 test, the missile fizzled out after a few seconds in the air. The second test in 2009 was seen as a technical failure, although it stayed airborne longer.

Michael Elleman, senior fellow for missile defense at the International Institute for Strategic Studies in London, said it looked like Gates “has stated a worst-case scenario.”

“A more likely one is, many more than five years,” Elleman said. North Korea’s current launch system “takes them a month to prepare, he added. “That’s not a combat-ready system.”

At the same time, Pyongyang has stoked Western concerns over its nuclear program. It revealed late last year it had made considerable progress in its uranium enrichment, potentially giving it a second route to make a nuclear bomb.

Still, experts say they do not believe North Korea is yet able to miniaturize an atomic weapon to place on a missile.

The new U.S. assessment comes amid heightened tensions on the Korean peninsula after a deadly attack on a South Korean island and the sinking of a South Korean warship last year.

Gates suggested South Korea’s patience with the North had run out, saying: “If there is another provocation, there will be pressure on the South Korean government to react.”

“We consider this a situation of real concern and we think there is some urgency to proceeding down the track of negotiations and engagement,” Gates said, while again conditioning any talks on a show of North Korean sincerity.

“But we don’t want to see a situation that we’ve seen so many times before, which is: the North Koreans engage in a provocation and then everybody scrambles diplomatically.”

TALKS WITH THE NORTH?

After threatening the South with nuclear weapons last month, the North has made almost daily offers since the start of the year to return to the negotiating table.

South Korea, which has called the offers “propaganda,” on Monday called for South-North Korean government meeting to confirm the North’s sincerity.

Gates suggested North Korea could demonstrate its sincerity with a moratorium on missile and nuclear testing. The U.S. official said a return by the International Atomic Energy Agency, the U.N. nuclear watchdog, was another key step.

The North responded Tuesday by declaring the only way for the two Koreas to work out their differences was to sit down first at a table to test each other’s resolve to iron out differences through talks.