|Kan's ratings fell steeply, following the prolonged nuclear crisis, triggered by a tsunami in March [REUTERS]
Japan's under-fire prime minister is expected to offer to resign later this month amid criticism over this handling of the country's nuclear crisis and recovery from a devastating earthquake and tsunami that left thousands dead.
Naoto Kan, who has been in office for slightly more than a year, told ministers on Tuesday that he expected his successor to be appointed on August 30, according to Japan's Kyodo news agency.
Kan hopes to steer two key bills on bonds issuance and on promoting renewable energy through parliament before stepping aside. Parliament is expected to vote on those bills by Friday, according to Japanese media.
His centre-left Democratic Party of Japan (DPJ) swept to power in a landslide election two years ago, ending more than half a century of almost unbroken conservative rule, but its term since then has been troubled.
Kan's ratings fell steeply in recent months, following the prolonged nuclear crisis, triggered by the country's earthquake and tsunami in March which killed thousands of people.
Seiji Maehara, the popular ex-foreign minister, was expected on Tuesday to announce his candidacy to replace Kan as prime minister.
Maehara, once dubbed 'Japan's Tony Blair' for his telegenic charm and ease before the cameras, is from the conservative wing of the ruling party and known for his strong stance towards China and North Korea.
An announcement by Maehara, expected in the early evening, would pit him against the favourite so far, Yoshihiko Noda, currently the finance minister, in the contest for the leadership of the DPJ.
"I'm resolved to stake my political life (on the party election). I want to run," the Nikkei financial newspaper reported that Maehara told supporters.
At 49, Maehara would become Japan's youngest post-war prime minister if he were to win the party presidency in a vote scheduled for next Monday, to be followed by parliament's confirming the new premier on Tuesday.
Maehara's profile rose last year when he was at the forefront of a bitter territorial dispute with Asian rival China that went on for months and plunged Beijing-Tokyo relations to their lowest point in years.
He is also known for his strong stance on communist North Korea, which has faced pressure from Japan over its nuclear and missile programmes and the past kidnappings of Japanese nationals.
Maehara's stint as foreign minister abruptly ended in March, days before the earthquake, tsunami and nuclear disaster hit Japan.
He stepped down after admitting he had received around $3,000 from an ethnic Korean who is not a citizen - a family friend who runs a restaurant - in contravention of Japanese political funding laws.
Still a politician, he has kept a relatively low profile in the five months since the March 11 disaster.