TOKYO • Japanese Prime Minister Shinzo Abe told US President Donald Trump that the strengthening of their two nations' alliance would be maintained even after Mr Abe's departure from office, a Japanese government spokesman said yesterday.

Mr Abe announced last Friday that he was resigning because of poor health, his long-running battle with ulcerative colitis ending his tenure as Japan's longest-serving prime minister.

"He wants President Trump to rest assured because the policy of bolstering the Japan-US alliance will remain unchanged," Deputy Chief Cabinet Secretary Akihiro Nishimura said.

Mr Nishimura was speaking to reporters after a 30-minute telephone call between Mr Abe and Mr Trump early yesterday.

Mr Trump called Mr Abe the "greatest prime minister in Japan's history", according to a White House spokesman.

Mr Abe also told Mr Trump that Japan would like to cooperate closely with the United States as it draws up a new missile defence strategy, Mr Nishimura said.

In a Twitter post yesterday, Mr Abe wrote: "Donald, thank you for honouring me with your kind words. Since I first met you at Trump Tower in New York four years ago, we have developed a deep relationship of trust and had so many bilateral meetings and phone calls.

"Our partnership has made the Japan-US relations more robust than ever before. My friendship and trust with you, Donald, means so much. I appreciate your friendship from the bottom of my heart."

White House spokesman Judd Deere said Mr Trump told Mr Abe he had done a "fantastic job" and that the relationship between their two countries was stronger than it has ever been.

REUTERS