Progress has been slow in drawing up a new U.N. sanctions resolution to punish North Korea for its fourth nuclear test as the U.S. and China disagree over its content, a South Korean official said Monday.

Washington has presented a draft resolution to Beijing for review, hoping to impose tougher and more extensive sanctions on Pyongyang for its Jan. 6 nuclear test.

Beijing showed an "initial response" to the draft last week and talks have begun in earnest, but progress has been slow, the official said.

"The Chinese side, as has been the case in the past, is extremely slow at first," he told reporters on the condition of anonymity as the talks are still under way.

Beijing's cooperation is essential in drawing a strong sanctions resolution from the U.N. Security Council because it is one of five veto-wielding permanent members, along with the U.S., Russia, France and Britain.

China, however, has been reluctant to push the North too hard out of concerns for its own security interests.

U.S. Secretary of State John Kerry is scheduled to visit Beijing later this week to step up pressure on China. China is believed to have more leverage over Pyongyang than any other nation as it props up the neighboring country's moribund economy.

Quoting the words of U.S Ambassador to the U.N. Samantha Power, the official said Washington and Beijing have so far failed to narrow their gap over the details of the resolution.

Laying out South Korea's diplomatic strategy this year, President Park Geun-hye proposed last week that multilateral talks on North Korea's nuclear program resume without Pyongyang.

China and Russia have long opposed the idea, saying it could antagonize the North.

"Because the situation has worsened following the fourth nuclear test, the president was stressing the need for five-party talks," said another government official, also speaking on the condition of anonymity. "It's a message to China and Russia, and especially China"

South Korea is seeking the five-way meeting in a bid to help revive the six-party talks that have been deadlocked for more than 7 years, he added.

He said South Korea has also pushed for three-way talks with China and the U.S. because of the symbolic significance that would have and the additional pressure it would put on the North, but that Beijing has resisted that too for similar reasons.

The six-party format brings together the two Koreas, the U.S., China, Japan and Russia. Its effectiveness has been increasingly called into question amid the North's continued provocations.

The official emphasized the importance of restarting "significant" six-way talks to focus on denuclearizing the North. (Yonhap)