Washington: US President Donald Trump has continued to reach out to allies in Asia to secure their co-operation to pressure North Korea over its nuclear and missile programs.

Mr Trump spoke to Thai Prime Minister Prayut Chan-o-cha and and his Singapore counterpart, Lee Hsien Loong, in separate phone calls about the North Korean threat and invited both of them to Washington, US officials said.

"They discussed ways to maintain diplomatic and economic pressure on North Korea," one US official said of the calls, speaking on condition of anonymity.

Mr Trump's calls to the two Asian leaders came two days after North Korea test-launched another missile that Washington and Seoul said was unsuccessful but which drew widespread international condemnation.