The ruling coalition has decided not to extend the current legislative session, which means the Upper House election will almost certainly be held July 21, senior lawmakers said.

The Liberal Democratic Party and its junior partner, New Komeito, have concluded it is unnecessary to keep the Diet open beyond June 26 now that it has paved the way for passing key bills, including one on vote-value disparities, the lawmakers said over the weekend.

The terms of half of the Upper House will expire July 28. Given the minimum amount of time required between the announcement of the election date and election day, the voting will almost certainly take place July 21, the lawmakers said.

Prime Minister Shinzo Abe, who heads the conservative LDP, has already been drawing up campaign strategies predicated on the assumption that he won't need to extend the Diet session, one of the senior lawmakers said.

LDP Secretary-General Shigeru Ishiba said in a speech Saturday in the city of Saga that the election will be announced July 4 and voters will go to the polls July 21 "unless extraordinary circumstances arise."