Secretary of State Condoleezza Rice cautioned North Korea on Friday that a second nuclear test "no doubt would deepen its isolation."

Rice and South Korea's foreign minister, Song Min-Soon, agreed at a State Department news conference that their governments want negotiations on North Korea's nuclear program resumed.

"If North Korea is prepared to return in a more constructive spirit" the talks could be reopened fairly soon, Rice said. But she added, "We know of no substantive response from the North Koreans."

The South Korean minister said he had no indication that a fresh nuclear test by the North Koreans is imminent, following its initial blast last Oct. 9.

The talks, held last month in Beijing, would swap economic incentives and a U.S. assurance of respect for North Korea's security for cessation of the nuclear weapons program that produced a nuclear test nearly two months ago.