(Adds details from the Commerce Ministry statement)

By Koh Gui Qing

Aug 6 (Reuters) - China has halted its purchases of U.S. agricultural products and will not rule out levying import tariffs on American farm imports purchased after Aug. 3, the Chinese Commerce Ministry said early on Tuesday.

The moves by China represent the latest escalation in its trade row with the United States that has unnerved global markets and investors.

"Related Chinese companies have suspended purchases of U.S. agricultural products," China's Ministry of Commerce said in an online statement posted shortly after midnight in Beijing on Tuesday.

The Chinese Commerce Ministry did not disclose the value of U.S. agricultural imports that may be subjected to new import tariffs.

U.S. President Donald Trump ratcheted up tensions between the two countries last week when he vowed to impose a 10% tariff on $300 billion of Chinese imports from Sept 1, a decision China's Commerce Ministry said was a “serious violation” of the consensus struck by Trump and Chinese President Xi Jinping in Osaka in June.

"China's market capacity is large and it has bright prospects for importing high-quality U.S. agricultural products," the Commerce Ministry said.

It added that it hoped the United States would keep its promises and create the "necessary conditions" for bilateral cooperation.

The amount of U.S. farm products that China buys has been a sore point in its trade spat with the United States. Other issues of contention include the protection of intellectual property rights in China and Chinese exports of fentanyl and fentanyl-related substances, which U.S. officials say is the main source of a drug blamed for opioid-related overdose deaths in the United States. (Reporting by Koh Gui Qing in New York Editing by Susan Thomas)