Japan's two largest political parties failed to agree on a new prime minister, leaving the country adrift two days after Prime Minister Tsutomu Hata's resignation. The policy gap between the three blocs squabbling for power -- Hata's coalition, the conservative "Liberal Democrats" and the Socialists -- was so great that they could not even agree on when to hold more talks. Hata, meanwhile, stays on as caretaker and looks to be the second consecutive lame-duck premier Japan will send to the G-7 economic summit, to be held July 8 in Naples. The P.M.'s fall is considered bad news for the Clinton Administration; Hata had begun thawing relations between the U.S. and Japan.