The U.N. Security Council is making progress in efforts to put together a new sanctions resolution on North Korea, a U.N. source said Monday, suggesting that the United States and China are narrowing differences.

But the source said, however, it's unclear when a resolution would be adopted as differences still remain.

For more than a month since the North's nuclear test, the Security Council has been struggling in negotiations to come up with a new sanctions resolution on the North because China has been reluctant to impose harsh measures on Pyongyang.

Beijing has condemned the North's nuclear and missile tests but has been lukewarm about calls for a stern response. Analysts have long said Beijing fears that pushing Pyongyang too hard could lead to its collapse, instability on its border and the ultimate emergence of a pro-U.S. nation.

Chinese cooperation is key to putting together any meaningful punishment as it is one of the five veto-holding permanent members of the U.N. Security Council, and the main provider of food and fuel aid to the impoverished North.

In Beijing, sources suggested the possibility of adopting a resolution this week.

"There is a consensus between the U.S. and China on the need for moving swiftly," one source said. "I think the two sides could reach a certain level this week."

The source also said that China is making some move after the North's Feb. 7 missile test.

"It is unclear whether that's because of North Korea's missile launch or that's because it no longer can stall for time, but there has been moves" on the part of China, the source said.

Another source said that China's position has become a little stronger than before, adding that a new resolution under discussions is sure to be the strongest resolution ever on the North.

So far, the council has adopted six resolutions, six presidential statements and two press statements with regard to the North's nuclear and missile program. Of the six resolutions, four included sanctions on the isolated nation. (Yonhap)