BEIJING, March 18 (Xinhua) -- A Chinese mainland spokesperson Sunday said the signing of a Taiwan-related travel bill by the United States had sent a "gravely wrong signal" to "Taiwan independent" separatists.

"Once again, I would like to sternly warn Taiwan that relying on foreigners to build you up will only draw fire against yourself," said An Fengshan, spokesperson for the Taiwan Affairs Office of the State Council.

An said the bill had caused a severe blow to the complex and grave situation of cross-Strait relations and the peace and stability across the Taiwan Strait.

It was reported that U.S. President Donald Trump on Friday signed the "Taiwan Travel Act" that encourages visits between the United States and the island at all levels.

"We resolutely oppose it," An said, noting that the bill had severely violated the one-China principle and the three joint communiques between China and the United States.

Experts also expressed concerns over the cross-Strait stability and the China-U.S. relations since the report came out.

Guo Yongjun with China Institutes of Contemporary International Relations said the "Taiwan Travel Act" interfered in China's internal affairs and violated the one China policy which the United States has long been upholding.

Guo said "Taiwan independent" separatists should not pin their hopes on the United States and confrontation with the mainland will only lead to a dead end.

Ni Yongjie, deputy director of the Shanghai Institute of Taiwan Studies, pointed out that trying to hold China in check with the "Taiwan card" is good to none.