Takako Doi, leader of the Social Democratic Party, vowed Saturday to make her opposition party a force for the ruling camp to reckon with in its drive to safeguard the war-renouncing Constitution.

In a speech delivered at a one-day party convention, Doi, 71, said her party will continue to stand by the under-privileged while attaching greater importance to having women stand up to the tripartite ruling coalition of the Liberal Democratic Party, the New Komeito party and the New Conservative Party.

She also encouraged party colleagues to try their best in the upcoming contests.

"We gained some seats in the general election, but we just toed the line," she said. "We will only be able to build a firm basis for reviving our party by posting a strong result in next year's Tokyo metropolitan assembly race and the House of Councilors election."

During the address, she also expressed a hope to visit South and North Korea and Mongolia sometime between late summer and fall to propose working out a Northeast Asian nonnuclear zone treaty.

The SDP has called on Japan and the three countries to conclude such a pact.

The convention, held at the party's headquarters in Tokyo, adopted an action plan calling for uniting various pro-Constitution forces centered on the SDP, as well as converting the SDP into a "people's party" that depends less on the support of labor unions.

During the convention, the party appointed Kiyomi Tsujimoto, a 40-year-old female civic activist and House of Representatives member, as the party's policy panel chief.

The SDP won 19 seats, an increase of five, in the 480-seat Lower House in last month's general election despite the fact that the total number of seats in the lower chamber was reduced by 20.

The largest opposition force for decades, the SDP was on the verge of extinction after many members defected to the opposition Democratic Party of Japan, which was launched in September 1996.

The party regained some of its old vigor after going back to its roots by focusing on preventing the Constitution from being revised.