Japan holds evacuation drill amid tension from N. Korea

But China's Liu made clear last week that Beijing's top priority is to restart talks with North Korea and reduce tensions, rather than impose new sanctions.

The UN Security Council voted unanimously to add 15 individuals and four entities linked to North Korea's nuclear and missile programmes to a UN sanctions blacklist, but Chinese opposition blocked tougher new sanctions that the United States was pushing.

The U.N. Security Council first imposed sanctions on Pyongyang in 2006 over its ballistic missile and nuclear program.

"The regime's actions are manifestly illegal under worldwide law", Mattis said.

Mattis, however, went on to say, "We can not and will not accept unilateral, coercive changes to the status quo" in the South China Sea. "The longstanding alliance between the United States and Japan contributes to the peace and stability in the region".

China's claim in the South China Sea needs to be handled peacefully and through negotiations, not by island-building and placing weaponry on the resulting dry land, Mattis said. "We will pledge to work closely with China where we share common cause".

The defense chief spoke directly to concerns that the United States might grant concessions to China to ensure its cooperation on North Korea, saying the issue was not "binary" and that the USA would continue to pressure Beijing elsewhere.

The pair of Japanese Naval Vessels and US Aircraft carriers have introduced a joint drill in the Sea of North Korea on Thursday. In a question-and-answer session with his audience of national security experts from across the globe, Mattis was asked whether the USA might attack the North pre-emptively and without warning South Koreans in advance.

He repeated that the United States will continue working with the United Nations, allies and partners to increase diplomatic and economic pressure "until Pyongyang finally and permanently abandons its nuclear and ballistic missile programs".

"Sanctions are not a goal in itself but as long as DPRK doesn't stop its behavior, we'll have no other choice than reinforcing the pressure on the regime", Permanent Representative of France to the UN Francois Delattre told reporters Friday.

The new weapon is so complicated and hard to develop that only Russian Federation and the U.S. were in possession of such technology before, the The China Daily newspaper reports.

The U.S. has about 28,500 troops permanently based in South Korea, a defense treaty ally.

Mattis' views on North Korea and China were backed by other participants in the forum.

"Must Stop Modernization of Nuclear Strategic Assets", North Korea said Saturday it was interested in peace, but would not surrender its nuclear weapons as a condition for de-escalating the current tensions with the USA on the Korean peninsula.

"Moreover, we will take further steps to protect the USA homeland, as demonstrated by this week's successful ballistic missile defense test".

On Tuesday, the Pentagon shot down a mock intercontinental ballistic missile (ICBM) over the Pacific Ocean using the long-range interceptor missile, launched from Vandenberg Air Force Base in California.

Mattis, speaking at the first plenary session of the annual Shangri-La Dialogue in Singapore, also touched on the threat of terrorism to the region, emphasizing the need to "defeat extremist organizations wherever they attempt to establish roots".

  • Leroy Wright