A senior U.S. official urged South Korea on Tuesday, January 17, to reduce its crude oil imports from Iran, ratcheting up pressure on Washington's close ally to help confront Tehran over its nuclear program.

South Korea restricts financial dealings with more than 200 groups and individuals with suspected links to Iran's nuclear program. But Seoul, which relies on Iran for up to 10 percent of its oil supplies, hasn't yet said whether it will buy less crude oil from Iran.

"We're urging all of our partners to help us, to work with us in putting pressure on the government of Iran, to get it to negotiate seriously," Robert Einhorn, the State Department's special adviser for nonproliferation and arms control, told reporters in Seoul after a meeting with senior South Korean Foreign Ministry officials. "In particular, we're urging them to reduce their purchases of crude oil from Iran. We're urging them to unwind their financial dealings with the central bank of Iran," AP quoted him as saying.

South Korea's Foreign Ministry said the government hasn't decided yet on the U.S. request to cut oil imports from Iran. South Korea reportedly hopes that a loss in Iranian oil imports could be compensated for by imports from other countries.

South Korea also said in a separate statement Tuesday that it understands the purpose of U.S. sanctions against Iran and that it will cooperate to the best of its ability for the peaceful resolution of the Iranian nuclear problem.

China, the world's biggest energy consumer, remains unwilling to back an oil embargo against Iran. A Chinese deputy foreign minister said last week that China's trade with Iran has nothing to do with Iran's nuclear program.