TOKYO, Japan (CNN) -- Japan's Prime Minister Taro Aso will dissolve the lower house of parliament this month and call for general elections in August, the government said Monday.
Prime Minister Taro Aso, a former foreign minister, became prime minister in September.
Hours later, the main opposition party said it, along with three others, submitted a no-confidence motion against Aso and his Cabinet.
The lower house of the Diet will be dissolved the week of July 21; elections for new lawmakers will be held on August 30, said Jun Matsumoto, the chief Cabinet spokesman.
The beleaguered prime minister has faced increasing pressure from within his party, the conservative Liberal Democratic Party (LDP), to step down as his approval rating plummets amid Japan's worsening economy.
While the race for the Tokyo assembly does not affect the Diet, it was the fifth successive local election loss for the LDP -- and a further sign that Aso's party is losing the confidence of the populace.
The LDP holds the majority in the lower house, but not the upper house.
Sunday's defeat convinced some in the LDP that they must oust Aso as party leader before national elections that were scheduled for October, according to analysts.
With Monday's announcement, Aso has moved up the elections by two months.
Aso, an outspoken politician and a former foreign minister, became prime minister in September.
The last two prime ministers, both from his party, resigned after less than a year in office.
CNN's Junko Ogura contributed to this report.