Relations between the United States and China soured when Panamanian authorities in February took control of two ports previously operated by a Hong Kong-based conglomerate.

US Secretary of State Marco Rubio reiterated on Thursday accusations that China had detained Panama-flagged ships in response to the takeover, and voiced support for the Central American nation.

China's foreign ministry hit back on Friday, accusing Washington of seeking to undermine supply chains through the vital waterway, which connects the Atlantic and Pacific oceans.

"The US side's relevant remarks are complete fabrication... only exposing its own scheme to claim hegemony of the canal," ministry spokeswoman Mao Ning told a news conference.

"Ultimately, who is blatantly undermining the neutrality of the Panama Canal, damaging the stability of global industrial and supply chains through unilateral bullying and coercion?" she said.

The ministry had previously said the US accusations were "unwarranted" and that China's position on the port was "clear-cut" when asked about the alleged ship detentions.

Washington and Beijing have accused each other of seeking to control the Panama Canal, which handles about 40 percent of US container traffic and five percent of world trade.

A Panamanian court ruled in January that a contract that allowed the Panama Ports Company (PPC) -- a subsidiary of Hong Kong-based CK Hutchison -- to manage the Pacific port of Balboa and Cristobal on the Atlantic since 1997 was "unconstitutional".

China had threatened Panama with payback after the court's decision, while CK Hutchison filed a lawsuit against authorities over the ruling.