LONDON (AP) — Britain will trigger the formal process for leaving the European Union before April, Prime Minister Theresa May said Sunday, putting to rest weeks of speculation on the timing of the move.

May confirmed her plans in an interview with the BBC before a speech at her Conservative Party's annual conference in Birmingham.

"I will be saying in my speech today that we will trigger before the end of March next year," she said.

While the prime minister previously had hinted she planned to initiate Britain's EU exit early next year, many observers had speculated she would wait until France's presidential election ends in May.

Britain voted in a June referendum to leave the EU, but has not formally notified the bloc of its intentions by invoking the article of the EU treaty that would trigger negotiations. Doing so will launch two years of talks to work out the details of Britain's future relationship with the single market.

While the two-year timetable is mandated by the EU treaty, it can be extended by a unanimous vote of the remaining members of the bloc.

The prime minister also said she would ask Parliament to repeal the European Communities Act, which automatically makes EU rules the law of the land in Britain.

May said her government instead would incorporate all EU laws into British law and then repeal measures as necessary on a case-by-case basis.

"That means that the United Kingdom will be an independent, sovereign nation," she said. "It will be making its own laws."

May said that by offering a timetable now, she hopes to encourage the two sides to engage in preliminary work that would help the negotiations go smoothly once they begin. EU leaders so far have rejected any such discussions.

The president of the 28-nation EU's governing European Council, Donald Tusk, offered a tweet in support of her position. He had told her at a recent Downing Street meeting that the "ball is now in your court."

"PM May's declaration brings welcome clarity on start of Brexit talks," he tweeted Sunday. "Once Art. 50's triggered, EU27 will engage to safeguard its interests."

One of the biggest sticking points in any talks will be immigration. The free movement of labor is a founding principle of the EU, and millions of EU citizens live and work in Britain.

The perception that immigrants have strained public services and changed the face of many communities was a factor for many British citizens who voted to leave the EU. May said that she intends to heed public opinion on that point.

"Apart from the message of leaving the European Union, I think there was also a clear message from the British people that they wanted us to control movement of people from the EU coming into the UK, so we will deliver on that," she said.

Critics quickly pounced on the first tangible moves on the process in weeks. Conservative Anna Soubry, a former minister who is in the Tory pro-Europe wing of the party, told ITV that she was concerned that May would trigger the Article so soon, warning that companies such as Nissan might leave without a deal on the single market.

"Triggering Brexit as early as March really concerns me, troubles me hugely, because we won't have had the French elections, we won't have had the German elections, and I'm sorry, it is going to take a lot of time and effort to disentangle ourselves and get the right deal," she said.

"The other thing that's got to be said is this — this idea that we hold the cards and that the EU is going to come to us and say 'do you know what, we'll give you pretty much what you want', — the idea we're going to get anything like we've got now is rubbish."

The opposition Labour Party asked for more clarity on the proposals. Stephen Kinnock, a member of Parliament from Aberavon, said May has yet to say what leaving will mean in practice.

"The Brexit process will give this government more power to reshape Britain than any government has had since the Second World War," he said in a statement. "And yet what Brexit means is still unclear, and the government has no specific mandate for its negotiating position, assuming that it has one."