LONDON — Prime Minister Boris Johnson suffered a damaging setback Tuesday in his quest to take Britain out of the European Union, losing a critical vote in Parliament and putting his plans for Brexit on hold as Britain’s three-year struggle to resolve the issue continued to defy any solution.

Mr. Johnson’s latest defeat came only 15 minutes after his first victory in Parliament. Lawmakers granted preliminary approval to the withdrawal deal he struck with the European Union last week, a major step toward achieving the prime minister’s goal of Brexit and one that broke a string of defeats for him.

But the lawmakers refused in a crucial follow-up vote to put legislation enacting Britain’s departure on a fast track to passage, which could have enabled Mr. Johnson to meet his deadline of leaving the European Union by Oct. 31.

By blocking Mr. Johnson, Parliament has thrown the whole process into a legislative netherworld that could mean months of further delays to a process that the nation has long since wearied of and just wants to see end.

It is entirely conceivable that Mr. Johnson’s deal will kick around Parliament for weeks, potentially becoming encumbered with amendments that either Mr. Johnson or the European Union would reject as unacceptable. The best option then, analysts said, would be to give the voters a chance to make themselves heard in a general election.

The back-to-back votes captured the one-step-forward, one-step-back nature of the Brexit saga. While lawmakers endorsed the contours of Mr. Johnson’s plan — something they had never done for his predecessor, Theresa May — they balked at being stampeded into passing the necessary legislation in three days.

The European Union will now have to decide how long an extension to grant Britain. Mr. Johnson said after the votes that he would “pause” the legislation and call European leaders to deliver the message that Britain was not interested in another extension.

Earlier on Tuesday, he said that if the deadlock slipped into next year, he would rather pull the bill altogether and face the voters, calculating that he could still win a popular mandate for a swift Brexit.

But if the European Union offers only a short-term extension of a few weeks, Mr. Johnson might well continue battling for passage of his Brexit blueprint, betting that the pressure would increase on Parliament to pass a deal that its members had already shown support for in principle.

Some critics noted that the legislation — which runs to 435 pages, including annexes, and would have profound consequences for the future of the country — was going to have less time for scrutiny in the House of Commons than a recent bill prohibiting the use of wild animals in traveling circuses.

On a day that encapsulated both the high drama and recurring gridlock of the Brexit debate, Mr. Johnson tried to put a good face on the split decision, noting it was the first time a Brexit agreement won a Parliamentary vote.

“How welcome it is, even joyful, that for the first time in this long saga, this House has actually accepted its responsibilities together, come together, and embraced a deal,” Mr. Johnson said.

But he expressed dismay that lawmakers “voted for delay” and said the government would accelerate its preparations to leave the European Union without any deal. “One way or the other,” Mr. Johnson insisted, Britain will leave Europe with “this deal, to which this House has given its assent.”

Earlier in the day, Mr. Johnson said that if his government was thwarted by Parliament, he would pull the legislation and demand an election. “I will argue at that election, ‘Let’s get Brexit done,’” he said.

Whether Mr. Johnson is serious about shelving his own deal — or was simply using it as a threat to pressure wavering lawmakers — was open to interpretation. On Tuesday evening, officials suggested he was keeping his options open.

But it made for another day of political theater in the House of Commons, where lawmakers rose one after another to condemn the government’s strong-arm tactics or to plead for an end to the endless frustration of Brexit.

“The devil is in the detail,” said the leader of the Labour Party, Jeremy Corbyn, “and having seen the detail it confirms everything we thought about this rotten deal: a charter for deregulation across the board, paving the way for a Trump-style trade deal that will attack jobs, rights and protections.”

Labour lawmakers promised to push for a series of amendments to the deal that could act as a kind of poison pill — demanding that there be a second referendum on whether to leave the European Union or putting all of the United Kingdom into the European Union’s customs union. A provision like that helped torpedo Mrs. May’s withdrawal agreement with Brussels earlier this year.

“We will seek a very clear commitment to a customs union, a strong single market relationship, hard-wired commitments on workers’ rights, non-regression of environmental standards and loopholes closed to avoid the threat of a no-deal Brexit once and for all,” Mr. Corbyn said after the votes.

Former allies of Mr. Johnson complained about the government’s pressure tactics. Waving a doorstop-size bound copy of the bill, Rory Stewart, a member of the Conservative Party who was purged by Mr. Johnson after breaking with him on a no-deal Brexit, said, “This is a hell of a big document.”

“We cannot pretend” that this is enough time to scrutinize the bill, Mr. Stewart said. “This is our Parliament. We cannot do down our Parliament.”

The negative vote on the legislation leaves the European Union with a difficult decision because it is almost impossible for Mr. Johnson’s Brexit deal to be ratified by Oct. 31, the next deadline.

On Saturday, Mr. Johnson was forced to request a new delay to Brexit, until Jan. 31, but it is up to the leaders of the bloc to decide unanimously on whether — and for how long — to delay Brexit again.

European leaders share Britain’s fatigue with the process and want Mr. Johnson’s deal to go through. On Tuesday in Brussels, the outgoing president of the European Commission, Jean-Claude Juncker, declared that Brexit had been a “waste of time and energy.”

But they also want to avert any risk of Britain leaving without any agreement, because that would hurt some fragile economies in mainland Europe, albeit not as hard as Britain’s. After the vote in Parliament Tuesday, Donald Tusk, the president of the European Council, tweeted that he would recommend granting the British request for an extension “in order to avoid a no-deal Brexit.”

Giving Britain a deadline of a few weeks, until mid-November, would put pressure on Parliament to ratify the Brexit deal, but it would be high risk. If lawmakers were unable to agree on the plan, Mr. Johnson would be under no obligation to request a further delay, and a “no deal” Brexit could result.

So European leaders might recycle a tactic they have used before and make Mr. Johnson a conditional offer: Allow Parliament a little more time if the deal can be ratified — potentially getting Britain out of the bloc quickly — but keep open the possibility of a longer delay if that proves impossible.

When Parliament rejected Mrs. May’s deal for a third time, Mrs. May requested an extension until June 30. But European leaders offered something different — a delay until June 1 if the British did not take part in elections for the European Parliament, or until Oct. 31 if they did.

Mrs. May took the second option.

In the current circumstances, a delay until Jan. 31 could allow time for a general election, though Britain would almost certainly need a longer extension to hold a second referendum on Brexit. The difficulty for the European Union is that Parliament has so far agreed to neither of those options.

The fierce maneuvering in the hours leading up to the votes attested to the complex political crosscurrents of the Brexit debate, more than three years after Britons voted to leave the European Union.

Mr. Johnson lined up support for the first vote on the deal from a handful of members of the Labour Party, which, along with a solid showing by his fellow Conservatives, gave him an unexpectedly healthy margin of 329 to 299.

Yet he lost support from Mr. Stewart and other exiled members of the Conservative Party on the timing of the legislation. That, along with a rejection by Labour members and the Democratic Unionist Party, left him with a losing margin of 308 to 322 for securing final approval of the bill by Thursday.