China said on Tuesday that the United States and other countries should not expand on the latest U.N. sanctions imposed on Iran over its nuclear programme.

China did not exercise its veto power last month when the U.N. Security Council approved sanctions that target Iran’s Revolutionary Guard, ballistic missiles and nuclear—related investments.

The United States followed that up when President Barack Obama signed a bill on Thursday that imposed tough unilateral sanctions against exports of gasoline and other refined petroleum products to Iran. It bans U.S. banks from doing business with foreign banks providing services to Iran’s Revolutionary Guard.

“China supports the U.N. sanctions. China believes that countries should have correct implementation of the sanctions instead of expanding the sanctions,” Foreign Ministry spokesman Qin Gang told a news conference.

The U.N. sanctions seek to punish Iran for rejecting proposals to halt uranium enrichment and take its nuclear fuel from abroad. The West and its allies fear Iran is developing nuclear weapons, though Iran says it is seeking nuclear power only for peaceful energy and medical research purposes.

As a permanent member of the Security Council and key Iranian ally, China could have vetoed the sanctions, but after considerable international pressure it agreed to support them.

But China has said its support for sanctions should not block efforts to find a diplomatic solution, and has called for renewed attempts to bring Iran back to the negotiating table.

China’s bilateral trade with Iran reached at least $36.5 billion last year. Iran meets 11 percent of China’s energy needs and Chinese companies have major investments in Iranian energy extraction projects and the construction of roads, bridges and power plants.

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