South Korean President Moon Jae-in and U.S. President Donald Trump agreed in a telephone call on August 7 to apply maximum pressure and sanctions on North Korea, as Pyongyang defiantly vowed to bolster its nuclear arsenal.
During an hour-long phone conversation, Moon and Trump said they would continue cooperating to rein in Pyongyang, particularly ahead of a regular joint military drill set for late August, Moon's spokesman Park Su-hyun told a media briefing.
In a separate statement, the White House said the two leaders "affirmed that North Korea poses a grave and growing direct threat" to most countries around the world.
The UN Security Council on August 5 unanimously imposed new sanctions on North Korea, aimed at pressuring Pyongyang to end its nuclear program.
Russia and China, longtime defenders of North Korea on the council, voted in favor of the measures.
The sanctions could slash North Korea's $3 billion annual export revenue by one-third, in what Nikki Haley, the U.S. Ambassador to the UN, called "the single largest economic sanctions package ever leveled against" North Korea.
In a further push, the United States, Australia, and Japan on August 7 urged the international community to pressure North Korea to abandon its "threatening and provocative path" and apply additional diplomatic and economic measures on Pyongyang over its missile tests.
Foreign ministers from the three countries issued a joint statement at the end of a meeting on the sidelines of the ASEAN regional security summit in Manila, saying the new sanctions on Pyongyang should be strictly implemented.
North Korea reacted defiantly, with Foreign Minister Ri Yong Ho saying Pyongyang is ready to give the United States a "severe lesson" with what he called its strategic nuclear force if Washington takes military action against it.
In a transcript of a statement that was distributed to media in Manila, Ri called the new sanctions "fabricated" and warned there would be "strong follow-up measures" and acts of justice.
The statement said the UN sanctions would never force the country to negotiate over its nuclear program or to give up its push to strengthen its nuclear capability.
"We will under no circumstances put the nukes and ballistic rockets on [the] negotiating table," the statement said.
"Neither shall we flinch even an inch from the road to bolstering up the nuclear forces chosen by ourselves unless the hostile policy and nuclear threat of the U.S. against North Korea is fundamentally eliminated," it added.
Pyongyang test-launched two intercontinental balistic missiles last month as part of its efforts to acquire a long-range missile capable of striking anywhere in the mainland United States.
Both missiles were fired at highly lofted angles and analysts say the weapons are capable of reaching parts of the United States if fired at a normal, flattened trajectory.
China, North Korea's biggest trade partner and ally, has said it is committed to fully enforcing sanctions, but that sanctions are not a lasting solution.
In a statement, China's Foreign Ministry stressed that the new sanctions should avoid impacting permitted economic activities and cooperation as well as food and humanitarian aid.
China has also called for Washington and Seoul to help lower tensions by reining in their military activities and drills, and by withdrawing the Terminal High-Altitude Area Defense (THAAD) antimissile system.
The influential Global Times, published by the state-run People's Daily, said in an editorial that the United States needed to curb its "moral arrogance over North Korea."
Meanwhile, the U.S. State Department said Secretary of State Rex Tillerson and Defense Secretary Jim Mattis will host their Japanese counterpart in Washington next week to discuss regional threats.
The August 17 meeting will focus on how the two allies can "coordinate their response to the evolving regional security environment, and strengthen their bilateral security and defense cooperation," a statement said. "The participants will also review the continued realignment of U.S. armed forces in Japan."
With reporting by Reuters, AP, AFP, and dpa