The EU's chief Brexit negotiator Michel Barnier on Tuesday said the bloc would do its utmost to meet a tight deadline and agree a post-Brexit trade deal with Britain before the end of next year."We will do the maximum," Barnier told reporters when asked if he could meet an eleven-month deadline to seal the trade agreement with Britain and avoid a no-deal divorce that could punish the economy.Prime Minister Boris Johnson on Tuesday threatened to outlaw any request to extend the transition period that begins when Brexit takes place on January 31 and runs to the end of the year.Asked to comment on Johnson's refusal to extend the talks if needed, Barnier said: "I have no comment to make on that. It is the British choice to choose the procedure it wants."Separately, EU commission executive vice president Valdis Dombrovskis warned the 11-month deadline "is going to be very limited" to forge an ambitious deal."It will be indeed rather problematic to hold negotiations and reach agreement on a comprehensive trade deal," he added, complaining that a "very rigid timeframe which reflects that certain things will be out of reach."