Health and Welfare Minister Junichiro Koizumi will officially announce his bid at a press conference later today, press reports said.

Neither Koizumi nor his staff could be reached for immediate comment.Koizumi would join Foreign Minister Keizo Obuchi and former Chief Cabinet Secretary Seiroku Kajiyama, who have already declared they want to become the ruling Liberal Democratic Party's next president.

The LDP president, who will be chosen on July 24 in balloting by party lawmakers, is virtually sure to become Prime Minister because the party controls the powerful Lower House of Japan's bicameral Parliament.

The party's choice could prove crucial in helping it regain the support of voters before Lower House elections, expected to be called some time before 2000.

Hashimoto announced he would resign on Monday afterthe LDP suffered a crushing defeat in elections for the Upper House of Parliament, losing 17 seats.

Analysts attributed the party's defeat to voter dissatisfaction with the way it handled the economy, which is mired in its worst recession since World War II.

Headlines in major newspapers said Koizumi, 56, decided to make a bid after securing the support of a key faction of LDP lawmakers. However, Obuchi, 61, appears to be the favourite of most party power brokers.