US President Donald Trump called several Asean leaders, including Singapore Prime Minister Lee Hsien Loong, over the weekend to discuss North Korea, said the White House.
A day after calling Philippine President Rodrigo Duterte, Mr Trump called Mr Lee yesterday, and was later scheduled to call Thai Prime Minister Prayut Chan-o-cha, to seek their cooperation in US efforts to rein in North Korea's nuclear and missile programmes, news reports said.
Mr Trump and Mr Lee both affirmed "the deep and longstanding relationship between Singapore and the United States".
"They expressed satisfaction that ministers from both sides are already working with each other and looked forward to meeting each other soon," said Singapore's Ministry of Foreign Affairs in a statement last night.
The calls came ahead of a meeting in Washington on Thursday between Asean foreign ministers and US Secretary of State Rex Tillerson.
The calls to regional leaders aimed to get "everyone in line backing up a plan of action" if the situation in North Korea deteriorated, White House Chief of Staff Reince Priebus told ABC News. "We need cooperation at some level with as many partners in the area as we can get to make sure that we have our ducks in a row," he added.
Pyongyang test-fired a ballistic missile last Saturday. The test appeared to have failed, in what would be the North's fourth successive unsuccessful missile test since March.
Asked about this on CBS last Saturday, hours after the missile test, Mr Trump would not rule out using military force against North Korea if it were to conduct a nuclear test, saying: "I don't know. I mean, we'll see."
While not once travelling abroad since his inauguration, Mr Trump has had 16 bilateral meetings with world leaders, including Japanese Prime Minister Shinzo Abe and Chinese President Xi Jinping.
Analysts say a less ideological and more transactional foreign policy has emerged from the calls and meetings, with Mr Trump pursuing personal relationships with the leaders.
Mr Priebus said Mr Trump was in regular contact with Mr Abe and had become "very close" to Mr Xi.
Meanwhile, the phone conversation between Mr Trump and Mr Duterte - their second since Mr Trump won the election - was said to be "warm" and "very friendly".
The duo discussed Asean's concerns about regional security, including the North Korean threat, and how the Philippine government was fighting hard to rid its country of drugs, "a scourge that affects many countries throughout the world", said the White House.
Mr Trump also invited Mr Duterte to the White House to discuss the US-Philippines alliance, "which is now heading in a very positive direction".
In a statement, Philippine presidential spokesman Ernie Abella said the discussion was warm, with Mr Trump expressing his understanding of the challenges facing Mr Duterte, especially on the matter of dangerous drugs.
Among Asean leaders, Vietnamese Prime Minister Nguyen Xuan Phuc had a brief phone call with Mr Trump shortly after his election win. And in late February, Mr Trump sent a letter to Vietnamese President Tran Dai Quang, saying he wanted to promote bilateral cooperation.
Mr Phuc is expected to make his first visit to Washington soon, and Mr Trump will be attending the Asia-Pacific Economic Cooperation meeting in Danang, Vietnam, in November, as well as the US-Asean and East Asia summits in the Philippines.