The former interior minister, who became prime minister without an election when her predecessor David Cameron quit after last year's referendum vote for Brexit, said she needed to strengthen her hand in negotiations which will reshape Britain and test the cohesion of the EU.
"The negotiations were meant to start in June regardless of the United Kingdom government (election) decision", he said when a journalist recalled the all-clear for negotiations is planned for late May.
The premier said she would campaign to make the UK's departure from the European Union a success and to "build a stronger Britain".
PM Theresa May reversed her longstanding promise not to go to the polls early.
The main opposition Labour Party welcomed May's election call, meaning that it is nearly a foregone conclusion that May will obtain the two thirds support she needs in the House of Commons for the election to be held.
The lawmakers approved the proposal, 522-13, after 90 minutes of debate to move the election up three years in a bid by the Conservative Party to expand its role in government and give better clout in negotiating Brexit.More news: Karen Handel Wiki: Facts to Know about Georgia's Former Secretary of State
May hit back that Labour offered only "bankruptcy and chaos", but denied she was complacent, saying: "We will be out there fighting for every vote".
The chief of the EU executive Jean-Claude Juncker and British Prime Minister Theresa May had a phone call Tuesday evening, following May's call for early elections in June, a European Commission spokesman told a news conference.
But as she spoke Mr Corbyn explicitly ruled out any post-election coalition with the SNP, insisting that he would not do a deal with Nicola Sturgeon's party to forge a so-called "progressive alliance", as hers was not a progressive party.
All said and done, however, whatever be the outcome of the election, Brexit is a reality from which there is no going back. In the first major opinion poll since the election was called, YouGov asked people who they would vote for if there was an election now.
With Jeremy Corbyn as prime minister we would see higher taxes, higher unemployment and a Brexit that fails to work for everyone.
By contrast, Labour has struggled to form a strategy over Brexit, while Corbyn's left-wing leadership is opposed by many of his more centrist MPs.More news: Huge comeback win as Cavs take 3-0 lead
The political and economic upheaval spawned by Brexit will require a strong government to tackle it and Theresa May is bracing herself for it in right earnest.
That approach risks satisfying neither its traditional working-class supporters, many of whom backed leaving the European Union, or its urban, pro-European members - leaving many commentators predicting an electoral disaster. The DUP campaigned for Brexit during last year's referendum while Sinn Fein has vowed to run on an anti-Brexit platform in the general election.
The stronger pound helped to push down Britain's main share index, which was headed for the biggest one-day drop since June 27, days after Britain voted to leave the EU.
Like nearly everyone else in Britain, the election announcement caught financial markets off guard, amid concerns of the economic implications of Brexit.
TRT World'sSarah Morice brings more from London.More news: North Korea's Missile Test Fails, US and South Korean Government Confirm
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