China said Thursday the European Union’s ban on oil imports from Iran is not a “constructive” response to Tehran’s suspected nuclear weapons program.

The EU announced the oil import ban on Monday, weeks after the United States announced a new set of economic sanctions aimed at pushing Iran to abandon its weapons program.

Beijing is a key ally of Iran, as well as the Islamic republic’s top oil customer. Chinese Premier Wen Jiabao defended his country’s purchase of Iranian oil Wednesday at a news conference in Doha, Qatar.

China says it “firmly opposes” Tehran producing a nuclear weapon, but has criticized the much tougher U.S. sanctions, saying they will lead to heightened tensions and drive up global oil prices.

Iran has threatened to block passage through the Strait of Hormuz in the Persian Gulf, which is a crucial shipping lane for global oil supplies, in response to the sanctions.

The new U.S. sanctions impose financial penalties against foreign banks that do business with Iran’s central bank, which is responsible for most of its oil deals.

Washington and four other permanent members of the United Nations Security Council — Britain, France, Russia and China — plus Germany, have been negotiating with Iran over its nuclear program. Tehran insists the program is strictly for peaceful purposes.