The U.N. Security Council is struggling to take what it calls "significant action" against North Korea for its latest nuclear test amid disputes among veto-wielding members, diplomatic sources said Sunday.

In the wake of Pyongyang's third known nuclear experiment on Feb. 12, the U.S. government called for a "swift, credible and strong" response by the U.N. council.

South Korea aims to release a tough sanctions resolution against North Korea within this month. Seoul holds the rotating presidency of the council in February.

But skepticism has grown about the likelihood of reaching a consensus on the issue by the end of this month.

"Throughout last week the U.S. and China had talks every day on the level of sanctions on North Korea, but there has been no progress," an informed U.N. source said, requesting anonymity.

The two sides had no meetings over the weekend, added the source.

The U.S. and its allies are seeking a resolution that includes a reference to Chapter 7 of the U.N. Charter.

A resolution based on Chapter 7 would obligate all U.N. member states to impose economic and other sanctions under Article 41 and even allow them to take military steps should Article 42 be adopted.

China is apparently opposed to any measure cornering its communist neighbor despite being critical of Pyongyang's provocative acts.

Chinese officials are also anxious about political and economic instability in North Korea that would lead to the exodus of refugees and damages to Beijing's regional security interests.

Many believe China uses North Korea as a buffer against the U.S. influence in Northeast Asia.

A tug-of-war between the U.S., supported by South Korea and Japan, and China backed by Russia, is a familiar pattern in the 15-member U.N. council in discussing a unified response to North Korea's nuclear tests and long-range rocket launches.

It took more than 40 days for the council to issue a resolution against Pyongyang for its December rocket launch.

In the resolution, the council vowed to take "significant action" in the event of a nuclear test by North Korea.

Some diplomats would not rule out the possibility that main players in the council will agree on a draft resolution on Monday or Tuesday and immediately circulate it to other members.

If that is the case, the council may be able to hold a plenary session within next week for the approval of the document, another U.N. source said. (Yonhap News)