One of the most-touted areas of the so-called opening up of China's economy remains a challenging market for some foreign giants.

With a flurry of announcements in 2018, Beijing loosened its control on the finance industry in what some called an "unprecedented" way. The moves came as complaints about unequal access for foreign players in the country escalated trade tensions between the U.S. and China. But amid ongoing negotiations, not many foreign companies have gotten full access to the massive Asian market yet.

On Monday, the Financial Times reported, citing two sources, that the People's Bank of China has not yet formally acknowledged applications from Visa and Mastercard to process yuan payments. The two companies filed the applications more than a year ago, and regulation says once the central bank acknowledges receipt, it must make a decision within 90 days, the FT report said.

"Mastercard's participation in China will benefit the country, its consumers and its digital payments development," the company said in a statement to CNBC. "We are engaging proactively and working closely with the PBOC to advance our application, and we remain committed to working with the Chinese government and businesses on growing the overall payments ecosystem over the long-term."

Visa did not respond to a CNBC request for comment.

The People's Bank of China referred CNBC to a statement shared with privately-run Chinese financial media site Wall Street CN. The comments from the central bank's head of payments said that Mastercard withdrew its application in June 2018 and that Visa's application from April 2018 still lacked some supplemental materials.

"Throughout the entire process, the People's Bank of China never raised the issue or requirement of a joint venture to operate in China," the central bank representative said, according to a CNBC translation of the Chinese-language report.

Approval would let the two U.S.-based companies compete in the local market with China's Unionpay. The company, which the FT report says counts the central bank as its largest shareholder, dominates the local market and has expanded overseas, giving it 36 percent of global market share in bank card payments, according to RBR research cited in the FT report. The article noted Visa and Mastercard have 32 percent and 20 percent of the global market, respectively.