By Michelle Nichols

UNITED NATIONS (Reuters) - The United States and China have agreed on new U.N. sanctions to impose on North Korea over the nuclear test it conducted in September, but Russia is delaying action on a draft resolution, a senior Security Council diplomat said on Wednesday.

The diplomat, who spoke on condition of anonymity, believed China could persuade Russia to agree to the new sanctions and that the 15-member Security Council could vote on the draft resolution as early as next week.

Since North Korea's fifth and largest nuclear test on Sept. 9, the United States and China, a close ally of North Korea, have been negotiating a new draft Security Council resolution to punish Pyongyang.

That draft text was recently given to the remaining three permanent council veto powers - Britain, France and Russia.

"The (permanent five members) are getting very close to agreement on a draft resolution," the diplomat said. "The key thing is that China and the U.S., who have led this, have got to a position that they agree on. So the issue now is Russia.

"The Russians are trying to hold it up but the Chinese are comfortable with it in terms of content," the diplomat said.

Two other council diplomats confirmed China has agreed to new sanctions but that Russia had some issues.

In Beijing, foreign ministry spokesman Geng Shuang said China supported further action being taken by the Security Council in response to North Korea's nuclear test, but details of the draft resolution were still being discussed.

The senior diplomat said the draft resolution closes loopholes in sanctions imposed on North Korea by the council in March, following Pyongyang's fourth nuclear test in January.

It cracks down on North Korea's coal exports, the diplomat said, and lists new names for targeted sanctions of a global travel ban and asset freeze. The senior diplomat gave no further details.

In March the council banned the 193 U.N. member states from importing North Korean coal, iron and iron ore unless such transactions were for "livelihood purposes" and would not generate revenue for Pyongyang's nuclear and missile programs.

Coal is particularly important to the economic health of North Korea, as one of its only sources of hard currency and largest single export. Coal also is bartered for essentials, including oil, food and machinery.

(Reporting by Michelle Nichols; Additional reporting by Christian Shepherd in Beijing; Editing by Bill Trott)