US Secretary of State Rex Tillerson sought to build pressure on North Korea after securing a new round of United Nations sanctions as he launched into two days of high-level diplomacy Sunday.

Tillerson is in Manila for a meeting of the 10-nation ASEAN regional bloc, but all eyes will be on his one-on-one talks with his counterparts from Washington's great power rivals, Russia and China.

And he will also for the first time be in the same room as North Korea's Foreign Minister Ri Hong-Yo, who defied US attempts to isolate Pyongyang to attend the ASEAN regional forum.

Ahead of Sunday's talks, Tillerson visited the Manila American Cemetery and Memorial to pay tribute to more than 17,000 US and Filipino servicemen who died fighting as allies during World War II.

Then he and his senior aides sat down with Myanmar's minister of state for foreign affairs, Kyaw Tin, for the first in a series of bilateral meetings on the sidelines of the forum.

He is later expected to see Russia's Foreign Minister Sergei Lavrov, China's Wang Yi and South Korea's Kang Kyung-Wha -- all three key players in the North Korean nuclear standoff.

The State Department has previously ruled out holding any direct talks with North Korea's envoy Ri during Tillerson's stay in Manila.

Just hours before the meetings were due to start, the UN Security Council voted unanimously to back a US-drafted resolution to dramatically tighten the existing sanctions targeting North Korea.

The vote marked a victory for US moves to force the North to halt its development of a nuclear-armed missile that could threaten US cities, and took some pressure off Tillerson before his Manila meetings.

But the US envoy still wants to ensure that China, in particular, is ready to rigorously enforce the new trade bans and that Russia remains committed to the embargo despite other differences with Washington.

Having failed to persuade its Southeast Asian allies not to invite Pyongyang to the forum, US officials also want to use the platform to remind Kim Jong-Un's regime of its diplomatic isolation.