TOKYO, Oct 18 (Reuters) - Japanese Prime Minister Shinzo Abe's coalition is on track for a roughly two-thirds majority in Sunday's general election, a survey by Kyodo news agency showed, as its conservative rival led by Tokyo Governor Yuriko Koike appeared to lose momentum.

Japanese go to the polls on Sunday to elect representatives for the country's 465-member lower house, the more powerful of Japan's two-chamber parliament.

The Kyodo poll, conducted by telephone between Oct. 15-17, showed Abe's Liberal Democratic Party (LDP) poised to win about 280 seats in the 465-member lower house. Combined with its junior coalition partner Komeito, it is likely to retain about two-thirds of the seats, Kyodo said.

The ruling bloc held a two-thirds "super majority" before the chamber was dissolved for the snap election.

About two-fifth of voters polled were still undecided, suggesting they could still sway the results, it said.

The Party of Hope, which Tokyo Governor Koike launched last month as a "reformist, conservative" alternative to the LDP, has lost momentum since the previous survey, Kyodo said.

The Constitutional Democratic Party of Japan (CDPJ), formed this month by liberal members of the Democratic Party, is set to beat out the Party of Hope to become the leading opposition party, at least doubling its representation, Kyodo added.

A Reuters corporate survey published on Wednesday showed Japanese companies overwhelmingly want Abe's coalition to stay in power but also want it to lose seats, suggesting they want political stability but don't want to hand him a landslide victory. (Reporting by Chang-Ran Kim; Editing by Michael Perry)