Beijing Saturday slammed a new US defence act, which includes measures to strengthen Washington's ties with Taiwan and support for Hong Kong's pro-democracy protestors, saying it "blatantly interfered" in China's internal affairs.
The tough-worded statement by China's top lawmaking body comes a day after President Xi Jinping told his US counterpart Donald Trump that US comments and actions regarding Taiwan, Hong Kong, Xinjiang and Tibet were harming ties between the two economic giants.
Beijing and Washington have agreed to a temporary truce in their bruising trade war, with a phase-one deal that has rolled back tariffs on billions of dollars worth of goods.
But China has come under strong criticism in Congress, including from Trump's Republican party, over its attempt to clamp down on pro-democracy protests in Hong Kong.
There is also growing concern in Washington, among both Democrats and Republicans, over the mass repression of ethnic Uighurs, a mostly Muslim minority in northwest China's Xinjiang region.
The National Defense Authorization Act (NDAA) calls for a report on the treatment of minorities in Xinjiang and to improve military ties with Taiwan, which Beijing regards as a renegade province awaiting reunification, by force if necessary.
You Wenze, a spokesman for the Foreign Affairs Committee of China's National People's Congress (NPC), told state-run Xinhua news agency, that the bill "blatantly interfered" in China's internal affairs.
The parts relating to Taiwan undermined peace and stability across the Taiwan Strait, he said.
Trump signed the $738 billion bill into law on Friday. It also calls for support for Hong Kong's pro-democracy protestors.
Washington's attempts to interfere in other countries' domestic affairs using so-called democracy and human rights would be in vain, You told Xinhua.
He expressed "resolute opposition" to the bill, the Xinhua report said.
The statement echoes the language used during a Xi-Trump phone call on Friday.
"China expresses serious concerns over the US side's recent negative words and actions on issues related to China's Taiwan, Hong Kong, Xinjiang and Tibet," Xi said during the call, according to Xinhua's summary.
Xi "noted that the US behaviours have interfered in China's internal affairs and harmed China's interests, which is detrimental to the mutual trust and bilateral cooperation," the state-controlled outlet said.