"China's restrictive treatment of outside suppliers of financial information services places U.S. and other foreign suppliers at a serious competitive disadvantage," U.S. Trade Representative Susan Schwab said in a statement. "We have raised this matter with China repeatedly, yet the problem has not been resolved."
The requests trigger a 60-day consultation period. If the talks fail, the U.S. and EU can ask the World Trade Organization to launch a formal investigation.
The announcements come amid mounting tensions with China over its swelling trade surplus.
There was no immediate response from China's foreign and commerce ministries.
"Competitive and open financial services information markets are the lifeblood of a strong financial sector, but China's rules have tipped the balance against foreign companies," EU Trade Commissioner Peter Mandelson said in a statement.
Washington has long taken the lead in lobbying Beijing over market access and currency controls, but Brussels has become increasingly vocal as its trade deficit with Beijing has expanded. China's trade surplus with the EU surged by 42 percent in January, according to Chinese government figures.
In a case brought by the United States, the EU and Canada, a WTO panel ruled last month that Beijing improperly used tax policy to restrict imports of auto parts. The United States is pursuing separate cases over product piracy and what it says are limits on imports of U.S.-made books, CDs and DVDs.
The United States and EU say China violated free-trade pledges two years ago with rules that benefit its Xinhua News Agency at the expense of foreign financial information companies such as Reuters and Bloomberg.
"Financial market professionals in domestic and foreign banks, investment firms and other businesses in China need real-time access to this information from diverse sources - foreign and domestic - in order to make effective business decisions," Schwab said.
Xinhua is struggling to transform itself from a Communist Party propaganda mouthpiece into a competitive media company, but has had limited success. It began to compete directly with foreign companies when it launched its own service in June.
The service, dubbed "Xinhua 08," says it provides information on 20 major Chinese and foreign exchanges and data on currency, gold and futures markets, and 55 industries including metals, energy, and real estate.
But the new regulations make Xinhua both a competitor and regulator to its foreign rivals, requiring that data, videos and photos be funneled through Xinhua-approved distributors. Currently, the only approved distributor is a Xinhua subsidiary.
Xinhua vowed not to abuse its role as regulator. But in a submission to the WTO on Nov. 12, the United States questioned how Xinhua could be "both a major market competitor of, and the regulator of, foreign financial information service providers in China."
The United States urged Beijing to set up an independent regulator and to return to conditions of 1996-2006, allowing foreign suppliers to have direct business relations with clients.
China also formalized restrictions on The Associated Press and other foreign agencies, which have sought wider access to the market, especially ahead of the Beijing Olympics in August.
EU leaders are facing increased pressure over rising imports of low-cost Chinese textiles, shoes and other goods that European producers say are detrimental to their businesses and threaten European jobs.