TOKYO, Oct 26 (Reuters) - South Korea said on in Wednesday it had agreed with the United States and Japan that a resumption of nuclear testing by North Korea would have to be met with an "unparalleled" response.Washington and its allies believe North Korea could be about to resume nuclear bomb testing for the first time since 2017, but experts say they have few good options for preventing or responding to such a move."We agreed that an unparalleled scale of response would be necessary if North Korea pushes ahead with a seventh nuclear test," he told a joint news conference.North Korea has been carrying out weapons tests at an unprecedented pace this year, firing more than two dozen ballistic missiles, including one that flew over Japan.On mounting tensions over Taiwan, a self-administered island China claims as its own, Sherman reiterated the U.S. stance that it does not support Taiwan's independence, but said it would be doing whatever it could to support Taipei and work with Japan and South Korea to ensure it could defend itself."