London, March 29 (RHC-Xinhua) -- Britain has officially begun the historic process to leave the European Union (EU) as the letter signed by Prime Minister Theresa May was sent to leaders of the 28-member bloc.

"There is no turning back," May told the House of Commons.

Giving official notice under Article 50 of the Lisbon Treaty, the letter was delivered to European Council President Donald Tusk at noon.

The move came nearly nine months after the British voted for Brexit by a margin of 51.9 percent to 48.1 percent in a referendum.

By triggering Article 50 of the Lisbon Treaty, Britain and EU is expected to have a two-year process in which the terms of exit will be negotiated. Unless both sides agree to extend the deadline for talks, the UK will leave the European Union in March 2019.