China has vowed to protect its companies from proposed US tariffs targeting buyers of Russian energy, warning Washington that economic coercion and unilateral sanctions would ultimately backfire.

Speaking on Wednesday, Chinese Foreign Ministry spokesman Lin Jian responded to legislation introduced in the US Senate that would authorize tariffs of up to 100% on imports from the largest purchasers of Russian oil and natural gas, including China.

“China firmly opposes unilateral sanctions that have no basis in international law or authorization of the UN Security Council, and will take necessary measures to firmly defend the legitimate rights and interests of Chinese businesses and citizens,” Lin said.

“Practicing double standards and resorting to coercion and pressuring will eventually prove to be self-defeating,” he added.

The revised sanctions bill was introduced on Tuesday by the US Senate. It is an update to legislation originally proposed by the late Russia hawk Senator Lindsey Graham, who died of heart complications on Saturday.

If enacted, the measure would authorize US President Donald Trump to impose tariffs of up to 100% on goods imported from the five largest buyers of Russian oil and gas. China and India would be among the countries most heavily affected.

The proposal comes less than two months after Washington and Beijing signed a trade framework designed to ease months of tariff tensions following a trade war in which the US imposed duties of up to 145% on Chinese imports, while China responded with tariffs of up to 125% on American goods.

During the dispute, Beijing also restricted exports of rare earth minerals critical to US high-tech and defense industries, disrupting supply chains and forcing some American manufacturers to suspend production.