The United States has sent a guided-missile destroyer to Japan, just days after North Korea tested seven missiles over the Sea of Japan earlier this week.
Reports say the U.S.S. Mustin has the latest missile-tracking system available. It arrived at Japan's Yokosuka military base Saturday.
Military officials say the missile tracking system is the same system that was used to assess North Korea's missile launches Wednesday and Thursday.
But the offficials add that the ship was not sent in response to the launches.
With the addition of the Mustin, the United States now has eight vessels at Yokosuka with missile-tracking systems.
Meanwhile, top U.S. envoy on North Korea, Christopher Hill, says he supports a Chinese proposal for informal six-party talks on Pyongyang's nuclear weapons program.
He also said Saturday that the U.S. is willing to meet bilaterally with North Korea on the sidelines of those talks.
Hill is in South Korea on a tour of Asian nations, to build consensus on a response to the missile launches.
He again rejected a North Korean demand that Washington lift financial sanctions against Pyongyang before resuming nuclear negotiations.
Earlier, Hill's South Korean counterpart, Chun Yung-Woo, said the missile launches should be treated as an opportunity to restart the talks.
On Friday, diplomats at the United Nations said there will be no Security Council vote on a binding resolution authorizing sanctions against North Korea until at least Monday.
The United States, Japan, Britain and France co-sponsored the draft resolution.
It calls on member states to prevent the transfer to North Korea of any type of material that could be used in missiles or weapons of mass destruction.
It also instructs North Korea to immediately stop developing, deploying and testing ballistic missiles, and to return to six-party negotiations on its nuclear program.
Security Council veto-holders China and Russia had pushed for milder wording in the document.
But U.S. Ambassador to the United Nations John Bolton said sentiment among Council members for the stronger resolution was overwhelming.
President Bush said Friday he wants a diplomatic solution to the crisis, but recognizes that arriving at a common goal and message can be a slow and cumbersome process.