The president of the European Central Bank says both markets and the economy have been "resilient" in the wake of Britain's vote to leave the European Union.

But Mario Draghi cautioned members of the European Parliament in Brussels on Monday that the long-term effects of the breakup "will be much more difficult to foresee."

Draghi says much will depend on how long it takes Britain to negotiate a new relationship with the bloc that covers future trade conditions and other matters.

He added that "the longer the uncertainty about the outcome lasts, the more relevant the consequences will be."

The EU treaty gives Britain two years after giving notice of its departure to work out a new deal. The British government has said it won't give notice until next year.