U.K Prime Minister Theresa May made the request to EU Council President Donald Tusk in a letter, after the U.K. Parliament declined not to have a third vote on the agreement that May and EU officials had reached regarding how the U.K. and EU countries would move forward after Brexit, the term now used exclusively to describe this departure.

May had twice sought a vote of approval for the deal, and Parliament had twice voted it down,by large margins. Parliament had then rejected the so-called "No-deal Brexit," in which the U.K. left without any sort of agreement in place. The last vote on the matter was an expression of willingness by Parliament to seek an extension. May has made that request, seeking a delay until June 30.

Tusk has already responded, saying that any extension must be accompanied by support from the U.K. Parliament, echoing statements made earlier by European Commission President Jean-Claude Juncker, who has recently reiterated his position that negotiations on the matter had finished, as far as the EU was concerned.

If the European Council does not agree (and just one country's voting no would mean that they don't agree), then the March 29 deadline stands and the U.K. would leave the EU, with or without any kind of agreement. Already, officials from a few other countries have indicated a willingness to veto a move for an extension.