WASHINGTON, Oct. 30 (Xinhua) -- U.S. President Donald Trump said on Friday that the United States will suspend preferential trade benefits for certain Thai products under the so-called Generalized System of Preferences (GSP), effective Dec. 30.

"I have determined that Thailand has not assured the United States that Thailand will provide equitable and reasonable access to its markets," Trump wrote in a letter to Congress.

"Accordingly, I have determined that it is appropriate to suspend the duty-free treatment accorded under the GSP to certain eligible articles that are the product of Thailand," Trump wrote.

The GSP, the largest U.S. trade preference program, is designed to promote economic development by allowing duty-free entry into the United States for around 3,500 products from over 100 designated beneficiary countries and territories, according to the Office of the United States Trade Representative.