The four main opposition parties agreed Monday to jointly submit a no-confidence motion against Prime Minister Junichiro Koizumi's Cabinet.

The motion is expected to be submitted to the House of Representatives by the Democratic Party of Japan, the Liberal Party, the Social Democratic Party and the Japanese Communist Party before the current 192-day Diet session closes Wednesday.

The ruling coalition, led by Koizumi's ruling Liberal Democratic Party, is likely to vote down the motion, the first since Koizumi took office in April 2001.