Air Canada announced new twice-daily flights from Toronto to four under-serviced U.S. cities. (Stan Behal/QMI Agency)

Air Canada announced new twice-daily flights from Toronto to four under-serviced U.S. cities Monday in an attempt to strengthen the airlinešs position in the face of growing competition.

"The launch today of twice-daily flights from Toronto to Memphis, Cincinnati, Syracuse and Portland, Maine, reinforces Air Canada's position as the leading transborder carrier between Canada and the U.S.," Ben Smith, executive vice president and chief commercial officer, said in a statement Monday.

The announcement is part of Air Canadašs ongoing strategy to secure the top spot in the competitive domestic market, the company said. The airline has ramped up its daily flight service to California and Phoenix in recent weeks.

Monday's new additions will bring Air Canada, Air Canada Jazz and its tier three partners up to a total of 233 daily flights to 55 U.S. destinations from six Canadian airports.

Rival carrier WestJet is exploring code-sharing agreements that would boost its U.S. services after a deal with Southwest Airlines fell through last month.