Prime Minister Junichiro Koizumi said Wednesday Japan should hold off before imposing more economic sanctions on North Korea, depending on whether Pyongyang responds "seriously" to the international condemnation of its July 5 missile tests.

"First, North Korea should take the (U.N.) resolution and the (Group of Eight summit) chairman's statement seriously. I think it's better for us to wait and see," Koizumi told reporters when asked to comment on Chief Cabinet Secretary Shinzo Abe's remarks a day earlier that Japan is working on new sanctions, including banning cash flows to North Korea.

Koizumi again urged North Korea to return to the six-nation talks on defusing its nuclear threat and make efforts to become a member of the international community.

Chief Cabinet Secretary Shinzo Abe and U.S. Ambassador to Japan Thomas Schieffer agreed to closely cooperate on measures to be taken regarding North Korea following Saturday's adoption of the resolution condemning North Korea's missile launches, Foreign Ministry officials said.

In a telephone conversation with Abe, Schieffer said the United States will closely consult with Japan on how to respond to North Korea in the wake of the UNSC's unanimous vote on the resolution in New York and called on the Pyongyang to promptly restart the six-party talks, the officials said.

North Korea has rejected the resolution.

Schieffer, telephoned Abe, also expressed his gratitude for Japan's cooperation with the United States, attesting to their strong bilateral alliance, the officials said.

Abe, in response, thanked Schieffer for the U.S. support and said he wants to see their countries work together in implementing the resolution through additional sanctions to prevent the proliferation of North Korea's missiles, the officials said.

Schieffer also talked with Foreign Minister Taro Aso by phone earlier in the day and conveyed a similar message.