The final text agreed on by the council and obtained by the Associated Press expresses "deep concern" at North Korea's plan.
Churkin called it a "very good" statement and said he was pleased it had been adopted.
The statement also urges Pyongyang to return immediately to six-party talks on scrapping its nuclear weapons program.
Earlier, South Korean President Roh Moo-hyun said his government would send a "grave warning" to North Korea, while China has warned its ally North Korea of "serious consequences" if it carries out the test.
The U.S. ambassador to the UN, John Bolton, has warned North Korea to think carefully before conducting a nuclear test, saying that if North Korea does carry out a test "it will be a very different world the day after the test."
North Korea has said it needs nuclear weapons to stop any possible attack by the United States. Washington has said it has no intention of invading.
(AP, Reuters, AFP)