British Prime Minister Theresa May in the cabinet office signs the official letter to European Council President Donald Tusk invoking Article 50 and the United Kingdom's intention to leave the EU on March 28, 2017 in London, England. [Photo/Agencies]

Nine months after the divisive Brexit referendum last June, May will officially trigger Article 50 in the letter that will be hand delivered on Wednesday to European Council President Donald Tusk.

At the same time, in a statement to MPs in the Commons, she will pledge to get the right deal for everyone in Britain, including EU nationals living in this country, according to a Sky TV report.

"We are one great union of people and nations with a proud history and a bright future," she will say. "And, now that the decision has been made to leave the EU, it is time to come together."

By triggering Article 50 of the Lisbon Treaty, the 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, Britain will leave on March 2019.

Article 50 refers to the formal procedure by which an EU member state notifies the European Council that it intends to leave the bloc.