LONDON, Oct. 18 (Xinhua) -- British Prime Minister Boris Johnson launched an offensive Friday to win over more support ahead of a crucial vote on his Brexit deal in the House of Commons on Saturday.

Number crunching by major British news organizations suggest that currently Johnson is just a handful short of the 320 votes needed to guarantee success for the deal agreed by the European Union (EU) on Thursday.

The Financial Times say their arithmetic gives Johnson 318 votes, compared to 321 against.

Sky News predicted Johnson's tally could reach 316, just four short of the number needed to cross the winning line.

The Times said the decision Saturday hinges on how 55 undeclared or undecided MPs decide when they go into the voting lobbies Saturday.

Downing Street told the Times that Johnson would focus the next 24 hours on "selling a great deal and importantly selling the opportunity to parliament to get Brexit done."

The House of Commons has passed a law requiring Johnson to seek an extension of Britain's membership of the EU if no deal is agreed by the end of Saturday.