VALLETTA (Jan 24): Britain can discuss but not seal bilateral trade deals while it remains a member of the European Union, the deputy head of the bloc's executive, which will lead the technical negotiations on Brexit, said on Tuesday.

Frans Timmermans' words raised the prospect of obstacles and delays for Britain's plan to pursue trade pacts with the United States and other nations as it prepares to leave the bloc.

British Prime Minister Theresa May had promised to start the divorce proceedings in March — though the timing of the exit was called into question on Tuesday when a top court ruled she must first seek approval from parliament.

"It's a very simple legal situation," said Timmermans, First Vice-President of the European Commission.

"Everybody can talk to everyone, but you can only sign a trade agreement with a third country once you have left the EU. You can't do that before," Timmermans told reporters.

His comments seemed slightly less rigid that those of his boss, the Commission's President Jean-Claude Juncker, who said last year he did not like the idea of Britain negotiating trade agreements on its own while Brexit has not materialised.

The line has been echoed by Italy's Europe minister, Sandro Gozi, also attending a meeting of EU ministers and officials in Malta: "It is clear that trade is an exclusive competence (of central EU institutions on behalf of member states). As long as UK remains member of the EU, it should respect the EU law."

EU regulations give both sides two years from the moment the exit clause is triggered to negotiate and agree the divorce before it comes to fruition.