Japanese Prime Minister Shinzo Abe announced his plans to resign in a news conference Friday due to a chronic illness that has resurfaced.

He called the decision “gut-wrenching.”

Concerns about Abe's health have swirled since early summer and grew in the last two weeks when he made two visits to a Tokyo hospital.

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Abe, 65, has said he suffers from ulcerative colitis had it under control with treatment.

He said Friday he's on a new treatment that requires IV injections and while there is some improvement, there's no guarantee it will cure his condition. He made the decision to step down after treatment Monday.

Abe's term ends in September 2021 and he is expected to stay on until a replacement is elected and approved by parliament.

There are a slew of politicians eager to replace Abe.

Japanese Prime Minister Shinzo Abe speaks during a press conference at the prime minister official residence in Tokyo Friday, Aug. 28, 2020. Abe, Japan’s longest-serving prime minister, says he’s resigning because a chronic illness has resurfaced. (Franck Robichon/Pool Photo via AP)

Japanese Prime Minister Shinzo Abe speaks during a press conference at the prime minister official residence in Tokyo Friday, Aug. 28, 2020. Abe, Japan’s longest-serving prime minister, says he’s resigning because a chronic illness has resurfaced. (Franck Robichon/Pool Photo via AP)

Shigeru Ishiba, a 63-year-old hawkish former defense minister and Abe’s archrival, is a favorite next leader in media surveys, though he is less popular within the ruling party. A low-key former foreign minister, Fumio Kishida, Defense Minister Taro Kono, Chief Cabinet Secretary Yoshihide Suga, and economic revitalization minister Yasutoshi Nishimura, who is in charge of coronavirus measures, are widely speculated in Japanese media as potential successors.

He stepped down previously because of a health issue in 2007 after only serving one year in office. He was reelected in 2012.

Abe, the country's longest-serving prime minister, helped pull Japan out of recession in his second term but the country is struggling again amid the pandemic.

He wasn't able to formally rewrite the post-World War II U.S.-drafted pacifist constitution - one of his top goals for his time in office. He failed as well in his goals to normalize relations with North Korea and sign a peace treaty with Russia.

The prime minister been repeatedly criticized for his handling of the pandemic and has been upstaged by Tokyo's governor.

During his term, he focused on the economy, rebuilding Japan's military, being a larger player in international affairs and has built a strong relationship with President Trump. Still, his ultra-nationalism has riled the Koreas and China.

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Abe's grandfather Nobusuke Kishi was also prime minister from 1957 to 1960 and his great-uncle Eisaku Sato, served from 1964 to 1972.

The Associated Press contributed to this report.