A close encounter between a Chinese submarine and a US aircraft carrier last month could have escalated into an "unforeseen" incident, the Wall Street Journal reported, quoting a senior US Navy officer. The submarine came close to the USS Kitty Hawk during exercises last month underlining concerns about China's rapidly expanding navy and a potential change in the balance of power in the region. Adm. William Fallon, the commander of the US forces in the Pacific, confirmed the incident this week. It had not been previously disclosed by the US Defense Department. Jiang Yu, a spokesperson for China's foreign ministry, said she was unaware of any incident, the newspaper reported.