To ratchet up the pressure on North Korea and to underscore cooperation between Tokyo and Washington, the chief U.S. negotiator on North Korean issues agreed Monday with Foreign Minister Taro Aso on the need for the international community to unequivocally condemn Pyongyang's ballistic missile tests.

"We want to make it very clear that we are all speaking with one voice on this provocative action by the North Koreans," Christopher Hill told reporters after meeting with Aso at the Foreign Ministry.

Hill arrived Sunday after visiting China and South Korea to discuss North Korea's missile tests last week. One of the missiles was a long-range Taepodong-2 theoretically capable of reaching the U.S. mainland.