As recently as last week, the airline's website entries for Taiwan did not mention China, according to checks made by Reuters, and it was not clear when the change was made.

Self-ruled Taiwan is claimed by Beijing as Chinese territory, and has become one of China's most sensitive issues and a potential military flashpoint. China has been pressuring airlines around the world, including U.S. carriers, to refer to Taiwan, Hong Kong and Macau as part of China.

Air Canada spokeswoman Isabelle Arthur said the carrier's "policy is to comply with all requirements in all worldwide jurisdictions to which we fly." 

Air Canada is currently negotiating a joint venture with Air China which the Canadian carrier has previously said is expected to be completed in the spring.

Representatives of Japan Airlines, All Nippon Airways, Australia's Qantas Airways and Korean Air Lines said recently they all received a letter from China requesting changes to their sites' references to Taiwan.

The four carriers had not revised their websites as of Tuesday, according to checks made by Reuters.

Air Canada did not say whether it had received the letter from China.

Earlier this month, the United States, embroiled in a trade dispute with China, dismissed the country's efforts as a way to "impose its political views on American citizens and private companies."

Taiwan's foreign ministry said it was "deeply concerned" about Air Canada's move to refer to Taiwan as part of China on the website.

"Our representative office in Canada has already protested to Air Canada and expressed our government's solemn concern and has demanded a speedy correction," the ministry's statement said.

Canada has separate deals for air services with Taiwan and China.

A spokeswoman for Transport Canada said by email on Tuesday the department had not received any requests from Air Canada for changes to Canadian policy on Taiwan, or for changes to the Canada-Taiwan air transport agreement.

(Reporting By Allison Lampert in Montreal and Jess Macy Yu in Taipei; Additional reporting by Jamie Freed in Singapore, Byron Kaye in Sydney, Haejin Cho in Seoul and Minami Funakoshi in Tokyo; Editing by Bernadette Baum)

By Allison Lampert and Jess Macy Yu