NEW YORK - UN Security Council members on Tuesday discussed new strong measures against North Korea for testing a nuclear device, Japans UN Ambassador said, without specifying any ideas that could form the basis of a resolution. The new measures will add to the set of sanctions already imposed on North Korea in 2006 for its first nuclear test, Japans UN Ambassador Yukio Takasu following a first round of discussion by the 15-nation council during a closed-door session. But other ambassadors were tight-lipped about potential new sanctions, and diplomats said no written proposals had begun to circulate. All seven nations were said to have agreed on the need to send a strong message to North Korea. We are in agreement on the goals, said Susan Rice, the American Ambassador. But the Chinese ambassador, Zhang Yesui, deflected questions about how strong a resolution his country would support. What we discussed today are the content of a strong message based on what we have in Security Council resolution 1718 in 2006, the Japanese Ambassador said. Nobody said that what we have done so far, what we have agreed, has been enough. We need additional measures. The Japanese Ambassador said that North Koreas nuclear test on Monday was a clear, direct threat against Japans security and also a challenge to the Security Council. Takasu did not use the word sanctions to describe the new measures, and he declined to provide details of the discussion, saying that a new meeting was planned on Wednesday at UN headquarters. North Korea detonated a nuclear device on Monday, which registered on seismic stations around the world at least 4.5, stronger than Pyongyangs previous nuclear test in 2006. The Council on Monday swiftly agreed to strongly condemn the test and to begin drafting new measures aimed at preventing North Korea from gaining the technology to develop its nuclear programme any further. On Tuesday, Pyongyang responded to the worldwide condemnation, including criticism from Iran, by test-firing missiles. Late Tuesday, it fired an additional missile over the Sea of Japan. While UN diplomats in New York discussed the draft resolution, the United States called for tough measures against Pyongyang. We want a resolution that provides a strong response from the Security Council to this provocation of North Korea, acting State Department spokesman Ian Kelly told reporters in Washington. Kelly said the missile tests by North Korea on Tuesday were a further provocation, but said the United States was still willing to work with Pyongyang to resolve the dispute in the six-nation talks. Our patience obviously is not indefinite, but we feel the door does remain open, that we are ready to engage, Kelly said, urging North Korea to make the right choice and engage constructively. When North Korea exploded its first nuclear device in October 2006, the Council imposed wide-ranging sanctions on military-related hardware and technology, including equipment like tanks and combat aircraft, warships, missiles and missile-guidance systems. Those measures are in Resolution 1718. The sanctions since 2006 failed to deter North Koreas pursuit of nuclear and ballistic missile technology. The resolution instructed North Korea to abandon all nuclear weapons and existing nuclear programmes in a complete, verifiable and irreversible manner. The International Atomic Energy Agency (IAEA) in Vienna was asked to verify compliance. The Council in 2006 also demanded that the Pyongyang government stop further nuclear testing and launching of ballistic missiles. Governments were asked to take legal steps to immediately freeze funds, financial assets and resources that belonged to North Korea. The Council imposed a ban on travel by North Korean officials who were responsible for the countrys nuclear and ballistic missile programmes. Cargo ships suspected of transporting illicit nuclear materials or weapons of mass destruction to and from North Korea can be inspected by governments under the US-led 2003 Proliferation Security Initiative (PSI).