Efforts to adopt a new U.N. Security Council resolution expanding sanctions on North Korea have encountered a last-minute delay as Russia has yet to give its consent to the draft worked out between the United States and China.

The United States is stepping up efforts to win Moscow's agreement, a prerequisite for the resolution's adoption as Russia is a veto-holding permanent member of the council, with U.S.

Secretary of State John Kerry speaking twice by phone with his Russian counterpart, Sergei Lavrov, over the weekend.

The resolution, which significantly toughens sanctions on Pyongyang, was put together after nearly 50 days of painstaking negotiations between the U.S. and China amid Beijing's opposition to harsh measures against the communist neighbor.

The U.S.-China agreement had raised hope that the resolution could be adopted as early as last weekend. But Russia put a last-minute hold on it, saying it needs time to review the proposed resolution. Russia is the only member of the 15-member council that has yet to endorse the text.

Sources said that the draft can be formally adopted on Wednesday at the earliest. Its adoption could be delayed further should Russia demand changes to the text.

In a phone call with Kerry on Friday, Lavrov stressed sanctions should take into account the already bad human rights situation in the North and should not affect civilian ties between the North and its foreign partners.

"Lavrov pointed out that the international community's reaction should be firm and aimed at cutting off the channels supplying North Korea's nuclear missile programs but apart from that should take into consideration the current difficult humanitarian situation in that country and so should not inflict any damage on foreign partners' legitimate ties with it (North Korea) in civilian sectors of the economy," Russia's Foreign Ministry said, according to the TASS news agency.

Lavrov could also discuss the issue with U.N. Secretary-General Ban Ki-moon when they meet in Geneva on Tuesday.

In Washington, State Department spokesman John Kirby said that a review of the proposal is still under way.

"As far as I know, deliberations are still going on about a new resolution. I don't know the status of those deliberatations and I certainly wouldn't speak for internal conversations that are ongoing on a resolution that hasn't been adopted yet," he said.

"We still continue to believe that it's important for the international community to react in a robust fashion to the most recent provocations by the North, that it's important that the international community stay unified on a more robust set of measures," he said.

After reaching final agreement with China, U.S. Ambassador to the U.N. Samantha Power unveiled key points of the draft resolution, which include requiring U.S. member countries to inspect of all cargo going in and out of North Korea.

The resolution also bans the North's exports of coal, iron and other mineral resources, a key source of hard currency that accounts for nearly half of the country's total exports, while prohibiting all small arms and other conventional weapons from being sold to the North.

In addition, the resolution also calls for banning jet and rocket fuel supplies to the North, and grounding North Korean flights suspected of carrying contraband, and denying suspicious vessels carrying illicit items access to ports. (Yonhap)