European Union Chief Brexit Negotiator Michel Barnier speaks during a plenary session of the EU Parliament in Brussels, Belgium January 30, 2019. REUTERS/Francois Lenoir

BRUSSELS (Reuters) - The European Union will not reopen its Brexit Withdrawal Agreement, including the controversial Irish backstop, chief EU negotiator Michel Barnier said on Monday, but alternatives to the backstop could be worked on after Britain leaves.

In a tweet after meeting Dutch Prime Minister Mark Rutte in The Hague, Barnier said: “Full agreement that Withdrawal Agreement cannot be reopened. Backstop (is) only operational solution to address Irish border issue today. EU ready to work on alternative solutions during transition.”

Britain is due to leave the European Union on March 29 but the withdrawal treaty, which British lawmakers are refusing to ratify due to the backstop arrangements on trade, would let it maintain today’s relationship during a transition period until at least the end of next year and possibly a further two years.