Mattis says US committed to Asia-Pacific as allies seek clear policy

Mattis said that in a speech on Saturday to the annual Shangri-La Dialogue in Singapore he would talk about the "international order" needed for a peaceful Asia, a reference to countering North Korea's nuclear and missile program.

"At the Shangri-la dialogue I will emphasize (that) the United States stands with our Asia-Pacific allies and partners," Mattis told reporters on the way to the regional security forum.

"The Department of Defense is focused on strengthening alliances, empowering countries to be able to sustain their own security, and strengthening U.S. military capabilities to deter war," Mattis said.

He is expected to meet with his counterparts from a number of countries including South Korea, Japan and Australia. China's delegation is led by a retired major-general from the Academy of Military Science, according to the forum's program.

Trump has actively courted Chinese support on North Korea, raising concerns among Southeast Asian allies in the lead-up to the dialogue that Washington might allow China a freer rein elsewhere in the region.

The U.S. focus on North Korea has been sharpened by dozens of North Korean missile launches - the most recent of which was on Monday - and two nuclear bomb tests since the beginning of last year. Pyongyang has vowed to develop a nuclear-tipped intercontinental ballistic missile (ICBM) capable of hitting the U.S. mainland.

Japan's navy and air force began a three-day military exercise with two U.S. aircraft carriers in the Sea of Japan on Thursday adding pressure on North Korea to halt an accelerating ballistic missile program.

China's island construction

Mattis said he would talk about the need for countries to uphold international law, an apparent reference to Beijing's construction activities on disputed islets and reefs in the South China Sea.

China's claims to most of the South China Sea, through which about $5 trillion in ship-borne trade passes each year, are contested by Brunei, Malaysia, the Philippines, Taiwan and Vietnam.

Last week a U.S. Navy warship sailed within 12 nautical miles of an artificial island China has built on a disputed reef in the South China Sea, the first such challenge to Beijing in the strategic waterway since Trump took office.

The Trump administration has completed a broad review of U.S. options aimed at curbing North Korea's nuclear and missile program and leans more towards new sanctions and increased cooperation with Beijing.

Some Asian officials say worries about Trump's direction have been fueled by his unpredictable personal approach to policymaking and emphasis on his chemistry with Xi.

Since meeting Chinese President Xi Jinping in April, Trump has praised him for efforts to restrain North Korea.

"It is going to take time for the actions that China is taking to have affect in terms of North Korea," said David Helvey, a senior U.S. defense official dealing with Asian and Pacific security affairs.

The United Nations Security Council will vote on Friday on a U.S. and Chinese proposal to blacklist more North Korean individuals and entities after the country's repeated ballistic missile launches.