UPDATE 1-In testy leadership debate, UK PM Johnson promises to deliver Brexit

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MANCHESTER, England, Nov 19 (Reuters) - Prime Minister Boris Johnson promised on Tuesday to take Britain out of the European Union by Jan. 31 and to secure a new trade deal by the end of next year, trying to press home his message that only he can deliver Brexit quickly in a leadership debate.

In a testy debate with opposition Labour's Jeremy Corbyn before a Dec. 12 election, Britain's departure from the EU dominated the opening exchanges when both leaders trying to cast doubt over the other's pledges.

"We certainly will come out on January the 31st, because we have a deal ... that is oven ready," Johnson said in the debate, with Labour Party leader Jeremy Corbyn, broadcast by ITV.

Johnson is promising to implement the exit deal he negotiated with Brussels and lead Britain out of the EU within months.

Corbyn wants to negotiate a new exit deal and put it to a referendum within six months alongside the option to remain in the bloc. Corbyn said during the debate he would honour whatever the result of that vote was.

Polls put Johnson's Conservatives as much as 18 percentage points ahead of Labour, but the election is difficult to call because of pacts and alliances on both sides of the Brexit debate and voters' deteriorating traditional allegiances. (Reporting by Kylie MacLellan and Costas Pitas, writing by William James, editing by Elizabeth Piper)