The United States has issued a stern warning to China days before Chinese President Xi Jinping arrives in Washington for a state visit.

The warning was issued by National Security Adviser Susan Rice on Monday over China’s alleged incursions in cyberspace, the dispute over the South China Sea, and global currency markets.

“As my critics allege, I can be rather direct. I can assure you that President Obama will be just as direct when he meets with President Xi,” Rice said in a speech at George Washington University.

“Everyone has to play by the same rules, regardless of size or power; because that’s the way everyone can compete or be treated equally.”

She accused China of taking steps which “erode the international system or that slowly eat away at a rules-based order and universal rights.”

Washington has for years accused the Chinese government and military of conducting computer-based attacks against the US, including efforts to steal information from federal agencies.

Beijing says Washington’s cyber attack accusations are hypocritical, since intelligence leaks have revealed that the US itself is most active perpetrator of cyber espionage against foreign countries, especially against China.

The six-day visit by Xi, which will start with a visit to Seattle followed by a meeting with President Obama for a private dinner at the White House on Thursday, has been complicated by other issues as well.

China has held a US businesswoman for six months over accusations of "spying and stealing state secrets."

Sandy Phan-Gillis was captured while crossing the border to Macau at the end of a trip to China by a trade delegation from the Texas oil capital Houston.

"Sandy is not a spy or a thief," her husband Jeff Gillis said on a website that provides information on her and her case.

"Sandy has now been detained for over six months, and she has not been allowed to see or speak with friends, family, or even her lawyers in that time," according to the savesandy.org website.