The United States and China have agreed on tougher-than-expected U.N. sanctions on North Korea, if not "terminating," government officials here said Friday.

But they acknowledged the challenges inherent in enforcing the resolution likely to be adopted at the U.N. Security Council early next week.

It contains "unprecedented strong and comprehensive" sanctions on Pyongyang for its Jan. 6 nuclear test and a long-range rocket launch a month later, a South Korean official said.

"If the resolution is implemented, it would make North Korea's nuclear development difficult," he stressed.

The 22-page draft resolution "decides" mandatory inspections of all cargo going in and out of North Korea.

The previous U.N. resolution on the communist nation in 2013 "called on" member states to conduct inspections if they had "reasonable grounds" to believe that they were illicit goods.

Exports of all small arms and other conventional weapons to the North will be banned and global financial sanctions on its banks and assets will be greatly expanded, said the official.

It would also prohibit the supply of aviation oil, including rocket fuel.

U.S. Ambassador to the U.N. Samantha Power described it as "the strongest set of sanctions" imposed by the council in more than two decades.

The South Korean official said Power was comparing these latest sanctions to the U.N. sanctions on Iraq in 1990.

"The draft resolution goes beyond our expectations," he told reporters in the background. He avoided a direct answer to a question about whether it is the "terminating" resolution that South Korea has sought.

The other veto-wielding powers -- Russia, France, and Britain -- and 10 non-permanent members of the council have yet to approve the draft version. If there is no objection, the council will release a "blue text" for vote.

It's almost certain that the document on North Korea will be passed without any major revisions, given the decision-making practices in the council.

At issue is how well the additional U.N. sanctions will be implemented.

Possible loopholes include that a state will remain able to decide whether to inspect North Korean cargo as a matter of its sovereignty.

The previous four resolutions have failed to stop Pyongyang from developing its weapons of mass destruction program.

"It will be different this time from the past," the South Korean official said.

In particular, China has shown a resolve to not let the North take such grave provocative acts with impunity.

Beijing was gravely upset by the North's long-range rocket launch that happened while the Security Council was in the process of discussing the level of punishment for its nuclear test, added the official.

Russia's post-resolution attitude remains to be seen as well. Pyongyang and Moscow have stepped up efforts to improve bilateral ties.

"South Korea, in close coordination with like-minded nations, will concentrate efforts on making the resolution be faithfully implemented," the official said. "If so, it is expected to help change North Korea's strategic calculations."

He cited the Kim Jong-un regime's "byeongjin" policy of simultaneously developing nuclear weapons and promoting economic growth. (Yonhap)