The vote scuppers Johnson's hopes to finalize Brexit on an extraordinary "Super Saturday" session.

British lawmakers voted Saturday to withhold support for Prime Minister Boris Johnson's new Brexit deal until all the supporting legislation is passed. The vote scuppers Johnson's hopes to finalize Brexit on an extraordinary "Super Saturday" session.

It was a significant loss for Johnson, who had hoped for a Brexit finale in an extraordinary "Super Saturday" session. But it is not a fatal blow against his deal.

Minutes after the vote, Johnson pledged to the House of Commons, "no delays." The prime minister said he would seek approval of his Brexit deal in a session in the coming week.

Based on previous legislation, passed months ago, Johnson is now required to formally seek a three-month extension from the European Union.

Opposition leaders said Johnson is now required by law to seek a delay.

Johnson began his remarks on Saturday by thanking lawmakers for gathering on a Saturday for the first time in 37 years, the first time in a generation, since Britain fought in the Falklands.

The prime minister conceded that the Brexit debate - which he launched - has taken a toll. Since Britain voted in June 2016 to leave the European Union, he said, "friendships have been strained, families divided, and the attention of this house consumed by a single issue that has at times felt incapable of resolution."

Johnson said: "But I hope, Mr. Speaker, that this is the moment when we can finally achieve that resolution." The prime minister called his deal "a new and better way forward" for Britain and Europe.

The British leader needs to win 320 votes in Parliament to pass his Brexit deal. Number crunchers on Saturday morning said it was too tight to call, but could see pathways for him to win the support he needs.

In one of his last outings as Speaker of the House of Commons, John Bercow, once played a starring role in the Brexit drama, selecting which amendments can be voted on.

The successful amendment, from the Tory rebel Oliver Letwin, was designed to box Johnson in - so he cannot force Britain to leave the European Union until the British lawmakers have scrutinized and passed all necessary legislation for an orderly exit.

Analysts have called it "cunningly crafted." It won't stop Brexit - it is not really intended to. But it could slow it down and might have broad support from those who don't completely trust the new prime minister. Johnson's allies have branded the amendment another sneaky attempt by an obstreperous Parliament to defy the will of the people and gum up the Brexit trajectory.

Underscoring how the country remains deeply divided on Brexit, thousands of protesters spilled into London from across the county to demand a second referendum.

Saira Ramadan, 36, a lawyer, said that "this is our last real opportunity to make our voices heard as publicly as possible, and in large numbers."

Asked about the claim that people are exhausted by Brexit, she said, "It would be disingenuous of me to suggest that there isn't a feeling of Brexit fatigue . . . but that's not to say that should be a reason for those of us who feel strongly enough to take it lying down and give up because we want it done."

For more than a year, polls have shown that if there were a countrywide "do over vote," Britons would, by a narrow margin, opt to stay in the EU.

Polling firm YouGov reported that 30% of Britons favor Johnson's deal, 17% want to get out without a deal to manage the transition and 38% percent want to remain in the EU, with the final 15% unsure.

Johnson swatted away calls for a second referendum and was pressing lawmakers to get Britain out by the end of October, as he has promised many times, "do or die."

On the floor of the chamber, Johnson said Britain has long had a divided heart over Europe. It is skeptical, dubious and halfhearted about Europe's grand projects, for further integration, for more federalism on the continent, for a Europe-wide defense pact, for a unified economic policy.

"We are skeptical about European integration," he said, "But passionate about Europe."

Johnson warned those who sought an extension: "We must abandon the delusion that this House can delay Brexit again."

The prime minister said there's "no appetite" in Brussels for more delay.

Jeremy Corbyn, leader of the opposition Labour Party, said lawmakers should reject Johnson's deal.

"I also totally understand the frustration and the fatigue across the country and in this House," Corbyn said. "But we simply can't vote for a deal that is even worse than the one the House voted to reject three times."

One challenge for the prime minister: there has been scant time to scrutinize the Brexit deal Johnson struck with the EU, which could be to his liking.

Even some friendly lawmakers who support Brexit have complained they want to read the government's own economic analysis of the cost of Johnson's deal before they vote on it.

"His strategy has been the same as Theresa May's strategy," said Simon Usherwood, a professor of politics at the University of Surrey. "Present a deal, and then bounce, bounce, bounce it straight through. Before you know it, you've agreed something, and don't worry about the details."

May presented her withdrawal agreement to Parliament three times - and three times she was rejected.

On Saturday, now a backbencher, May rose to speak in the chamber and confessed a sense of deja vu. But she offered full-throated support for Johnson. If Parliament doesn't back the deal, May said, "it is guilty of the most egregious con trick on the British people."

Her voice rising with passion, May said, "If you don't want no deal you have to vote for a deal. Businesses are crying out for certainty. People want certainty in their lives."

Johnson - who has campaigned under the banner of "Get Brexit Done" - could have another factor working in his favor: "Brexhaustion." In a sign of the times, Sky News on Friday launched its own completely Brexit-free news channel, hoping there is a market for people who want a break from Brexit but not the news.

Johnson's new Brexit deal offers a more distant relationship with the EU than the agreement struck by his predecessor. However, his plan would see Northern Ireland stay largely aligned to the EU, even though it would leave the block with the rest of the U.K.

The Northern Ireland's Democratic Unionist Party said the deal was not in the province's "long-term interests." Its 10 lawmakers are expected to vote against the deal on Saturday.

"It was once said that no British prime minister could ever agree to such terms," DUP lawmaker Nigel Dodds said in Parliament. "Will he now abide by that and reconsider the fact that we must leave as one nation together?"

John Major and Tony Blair said in videos published for the People's Vote campaign that Johnson's deal risked derailing peace in Northern Ireland. The two former prime ministers, who both backed "remain" in the E.U. referendum, played important roles in the Good Friday Agreement, the accord that helped to usher in peace in Northern Ireland after decades of sectarian violence.

"It is a shame and an outrage frankly that Northern Ireland is treated like some disposable inconvenience to be bartered away," said Blair.

Over the past 48 hours, there has been much wheeling and dealing and arm twisting. It's hard to know what methods of persuasion, if any, were used in hopes of winning support. There was speculation that Johnson could offer the 21 lawmakers he expelled from his party last month a way back in if they voted to support his deal.

He also offered new pledges on Friday night to protect workers' rights, which was seen as an attempt to woo more Labour lawmakers, especially those who are either Brexiteers or who represent Brexit-backing constituencies.

Labour's Corbyn called those pledges "empty promises."

This deal, Corbyn said, would "absolutely inevitably lead to a Trump trade deal, forcing the U.K. to diverge from the highest standards and expose our families once again to chlorine-washed chicken and hormone-treated beef."

In an opinion piece in the Guardian newspaper, Melanie Onn, a Labour lawmaker from Grimsby, a pro-Brexit town populated by "Labour-leavers," implored her colleagues "to use this unique chance to help us move on."

"The risk of letting this final shot at a deal slip through our fingers is too great," she wrote, in a piece authored with a Conservative Party lawmaker.

Johnson is also hoping to bring on side the 28 hard line Brexiteers from his party who have previously been resistant to a Brexit deal. That group said Saturday morning that it had advised its members to vote for Johnson's agreement.

Andrea Jenkyns, a Conservative lawmaker who never once voted for May's deal, tweeted: "After much consideration, I have decided to back @BorisJohnson deal. Obviously I would prefer No-Deal but I believe we are in real danger of losing Brexit with the Remain shenanigans and the stakes are dangerously high at the moment."

Europian Union Boris Johnson, Brexit Deal, Super Saturday