Shinzo Abe prepares to step down even as his successors vie for Japan's top job

Japan's longest-serving prime minister, Shinzo Abe, was set to resign, national broadcaster NHK said on Friday, saying he wanted to avert problems for the government from a worsening health condition. Abe has battled the chronic disease ulcerative colitis for years. If Abe resigned, he would probably stay on until formally replaced, which requires the ruling Liberal Democratic Party (LDP) to pick a new leader to be formally elected in parliament. Here are details of some likely contenders to take the helm of the world's third-largest economy.

Finance minister Aso, 79, who also doubles as deputy prime minister, has been a core member of Abe's administration. Without a clear consensus on who should succeed Abe, LDP lawmakers could elect Aso as a temporary leader if Abe resigns.

A hawkish former defence minister and rare LDP critic of Abe, Ishiba, 63, regularly tops surveys of lawmakers whom voters want to see as the next premier, but is less popular with the party's lawmakers.

Kishida, 63, served as foreign minister under Abe from 2012 to 2017, but diplomacy remained mainly in the prime minister's grip. The low-key lawmaker from Hiroshima has been widely seen as Abe's preferred successor but ranks low in voter surveys.

Defence Minister Taro Kono, 56, has a reputation as a maverick but has toed the line on key Abe policies, including a stern stance in a feud with South Korea over wartime history. Educated at Georgetown University and a fluent English speaker, he previously served as foreign minister and minister for administrative reform.

Suga, 71, a self-made politician and loyal lieutenant since Abe's troubled term as premier in 2006 and 2007, was among a band of allies who pushed Abe to run again for the top post in 2012.

The name of Koizumi, 39, now environment minister and the son of charismatic former premier Junichiro Koizumi, is often floated as a future premier, but many consider him too young. He shares some of Abe’s conservative views and has paid his respects at Tokyo's controversial Yasukuni Shrine for war dead.