BEIJING (Reuters) - China said on Wednesday U.N. authorities should respect its judicial independence after a U.N. agency said last week that an American businesswoman who is accused of spying in China had been detained arbitrarily.

The U.S. State Department said it was concerned about the welfare of Sandy Phan-Gillis of Houston, Texas, who has been held for more than a year without formal charge. It urged China to resolve the case "expeditiously."

State Department spokesman John Kirby said that although the ruling of the U.N. Working Group on Arbitrary Detention was not legally binding, "we would encourage the Government of China to review and consider the opinion and recommendations received..."

Earlier, Chinese Foreign Ministry spokesman Hong Lei criticized the U.N. group after it said Phan-Gillis's detention violated international human rights norms and that authorities had not provided evidence for holding her without any specific charges.

"We hope that the U.N. Working Group on Arbitrary Detention can perform its duties impartially, respect China's judicial sovereignty and cease making irresponsible remarks about legal cases being handled by relevant Chinese departments," he told a regular briefing.

Kirby, who spoke at a regular news briefing in Washington, said senior U.S. officials had raised the case multiple times with the Chinese government and a U.S. consular officer last visited her on June 20. Kirby said China should ensure Phan-Gilles had full access to an attorney.

In a statement that cited an unidentified source, the U.N., working group said Phan-Gilles had not been allowed to speak to a lawyer or family members regularly and had recently been hospitalized after suffering a heart attack.

The group called for her to be released or granted access to legal counsel and given a fair trial.

Phan-Gillis was detained in March 2015, when she was stopped for questioning in the southern city of Zhuhai as she was preparing to depart for Macau through a border crossing.

China's state secrets law is extremely broad, encompassing everything from industrial data to top leaders' birthdays. Information can also be declared a state secret retroactively.

International organizations including the United Nations have criticized China's judicial processes for failing to guarantee the rights of the accused, including freedom from torture, and fair trials.

There is no independent oversight of China's law enforcement authorities or courts, which answer to the ruling Communist Party.

U.N. Secretary-General Ban Ki-moon is visiting Beijing this week.

(Reporting by Megha Rajagopalan in Beijing and David Brunnstrom in Washington; Editing by Robert Birsel, Bernard Orr)