The pressure on the unpopular Japanese prime minister Naoto Kan increased as the ruling party powerbroker Ichiro Ozawa hinted he will back a no-confidence motion against Kan, if he refuses to quit, said media reports on Tuesday.

Ozawa, known as the Destroyer for his record in shaking up politics in the past, told his followers he would push for Kan to quit on his own. But if Kan doesn't quit, he would back the no-confidence motion, said Kyodo news agency and other Japanese media.

Japan's main opposition Liberal Democratic Party (LDP) could submit a no-confidence motion to parliament as early as Thursday as Kan is struggling with the nuclear crisis. He has been failed so far to figure out how to pay for rebuilding the northeast region devastated by a March 11 earthquake and tsunami, and draft tax reforms to pay for rising social security costs, reported Reuters.

Except the tiny Social Democratic Party, all opposition parties have said they will back the no-confidence motion. However, according to analysts, it's not sure whether the LDP could manage to win over enough disaffected members of the ruling Democratic Party of Japan (DPJ) for motion to pass.

In order to secure passage of the motion, the opposition needs 70 or more of the 305 DPJ lower house members to defect. If it happens, Kan would be forced to resign.