President Donald Trump spoke to the leaders of Thailand and Singapore Sunday in separate phone calls about the rising security concerns in the Asia-Pacific region and invited both prime ministers to the White House to further strengthen ties between the U.S. and their countries, the White House said in two statements.

Trump and Thailand Prime Minister Prayut Chan-o-cha discussed their mutual desire for "peace and stability in the Asia-Pacific region," a White House readout said.

Trump and Prime Minister Lee Hsien Loong of Singapore “affirmed the deep and longstanding relationship between Singapore and the United States,” a statement from Singapore’s Ministry of Foreign Affairs said.

The White House issued a statement saying Trump’s invitation to Lee was extended to "further strengthen ties," noting that the partnership between the U.S. and Singapore is "marked by thriving trade and investment, robust security cooperation, and close collaboration on regional and global challenges."

Trump and Prayut also "expressed a strong shared interest in strengthening the trade and economic ties between the two countries."

The invitation comes amid heightened tension between the U.S. and North Korea over North Korea’s missile and nuclear programs. Trump is attempting to rein in North Korean leader Kim Jong-un but so far has been unsuccessful as North Korea test-fired another missile Saturday and has touted its progress in developing an intercontinental ballistic missile capable of reaching the continental United States.