Every American president has a favorite foreign leader. For Donald Trump, it seems to be Japanese Prime Minister Shinzo Abe.

The two leaders toasted their "bromance" on Monday as they wrapped up two days of golf, burgers and serious talks on trade and North Korea.

The two men have met face-to-face six times since Trump was elected U.S. president a year ago and had 16 telephone conversations. They've played golf twice, once at Trump's Mar-a-Lago resort in Florida and again on Sunday outside Tokyo.

Abe recalled how his grandfather, then-premier Nobusuke Kishi, and President Dwight D. Eisenhower began the tradition of U.S.-Japan golf diplomacy 60 years ago.

"When you play golf not just once but two times, the person must be your favorite guy," Abe said ahead of a formal banquet with Trump on Monday. He added that never had two Japanese and American leaders forged such a close bond in just one year.

Abe was the first foreign leader to meet Trump after his election last November, a win that caught Tokyo off guard after many had expected Democratic Party candidate Hillary Clinton to win and worried about Trump's "America First" rhetoric.

Trump told the dinner guests that for protocol reasons, he shouldn't have met a foreign leader before his inauguration--but when he tried to call Abe to wave him off, the Japanese premier was already on a plane to New York.

"We have to spend more time together because I enjoyed every minute of it even though he (Abe) is a very tough negotiator," Trump said. "We will be back soon."

Trump and Abe are hardly the only U.S. and Japanese leaders to bond. Ronald Reagan and Yasuhiro Nakasone set the gold-standard for friendly ties between leaders of the two allies back in the 1980s, when they famously called each other by the nicknames “Ron” and “Yasu”.

George W. Bush and Junichiro Koizumi also bonded during Koizumi’s 2001-2006 term as Japanese premier, playing ball, eating BBQ at Bush’s Texas ranch, and visiting Elvis Presley’s Graceland mansion, where Koizumi crooned Elvis tunes.

Diplomatic experts said the personal chemistry between Abe and Trump appeared real, but also noted that forging warm ties were in a way a diplomatic necessity for Japan, which ultimately relies on the U.S. nuclear umbrella for its security.