Japan's two biggest opposition political parties will merge in an attempt to end the ruling Liberal Democratic Party's decades of dominance. The announcement comes amid speculation about a general election before the end of the year.

Japan's main opposition party, the Democratic Party, and the second largest group, the Liberal Party, say they will merge before the end of September. Their leaders say they want to capture the attention of what they call Japan's disenchanted electorate before a general election widely expected in November.

The opposition leaders say they will capitalize on voters' unhappiness over Japan's stubbornly sluggish economy, which has led to high unemployment and a deflationary spiral that has sapped consumer confidence.

Naoto Kan, leader of the Democratic Party, says Japan needs real political leadership, which is not found in Prime Minister Junichiro Koizumi and his party, the Liberal Democrats.

Ichiro Ozawa, who heads the Liberal Party, says he aims to change the forces of political power in Japan.

There are indications that a sizable number of Japanese will back the new group. A poll by the Asahi newspaper released this week shows that Mr. Koizumi's popularity rating has dropped to 42 percent, down five percentage points from last month. Some political analysts say the merger could hasten a further drop. Thirty-seven percent of respondents also say they plan to vote for an opposition candidate in the coming election.

But unseating the Liberal Democratic Party is a challenge. The LDP has maintained its grip on power since it was established in 1955, except for one year in the early 1990's. It has a strong and loyal support base among farmers and several powerful industries. It also has more than twice the seats in Parliament than the two opposition groups will hold once they are combined.