The White House announced new rules on Monday aimed at opening the country to far more visitors, saying it will soon lift blanket travel restrictions on international visitors as long as they can show that they’ve been vaccinated.

The new rules will take effect in early November and will also subject visitors to new testing and contact-tracing procedures. Jeff Zients, the White House coronavirus response coordinator, said the new system would focus on whether an individual has been vaccinated rather than banning visitors from entire countries.

“We know vaccines are effective including against the delta variant, and vaccines are the best line of defense against covid,” Zients said. “So this vaccination requirement of course is the best tool we have in our arsenal to keep people safe and prevent the spread of the virus.”

The announcement is part of a stepped-up effort by the Biden administration to require people to get vaccinated and reward those who do. Recent changes include ordering all companies with more than 100 employees to require that their workers be vaccinated or get weekly coronavirus tests. Federal workers, service members and nearly all health workers will have to be vaccinated.

The fate of the Biden presidency relies on whether these measures work and the country returns to some semblance of normalcy, aides and Democratic strategists say.

The delta variant surge has significantly changed the president’s calculus on what he is willing to do to reopen the country, including widespread mandates which President Biden had initially said would be unnecessary.

Monday’s announcement, which European allies have demanded for months, leaves some crucial questions unanswered. Chief among them is how U.S. airlines will be able to tell if a foreigner is vaccinated and whether this new system will involve some kind of “vaccine passport” arrangement.

“The process and means for travelers to demonstrate vaccination status will be released by early November when this plan begins to be implemented,” White House spokesman Kevin Munoz said via email.

The Biden administration has been reluctant to create a national system of vaccine verification out of a concern that it would be politically controversial and pay into conservative complaints of government heavy-handedness.

The move also raises the question of whether the administration will create a similar system for domestic travel, particularly if vaccine rates do not change significantly despite the recent initiatives. Top White House aides have been split on whether vaccine mandates on domestic air travelers would be effective.

It also is not clear whether vaccines that have not been authorized in the United States, such as the Oxford-AstraZeneca shot or vaccines made by China and Russia, will be accepted. That will be determined when the details of the new rules are hammered out by federal agencies, White House aides said. Aides signaled Monday they would continue imposing new rules until the pandemic is beaten back.

“We clearly have a track record that shows we’re pulling available levers to require vaccinations, and we’re not taking any measures off the table,” Zients said.

The announcement came as Biden prepared to meet face-to-face this week with world leaders at the United Nations at a time of strained relations between the United States and Europe. European leaders have voiced frustration with the administration’s handling of the pullout from Afghanistan, while France is enraged by a U.S. deal to sell nuclear submarines to Australia that it considered to undercut its own agreement with that country.

It is unclear if those tensions pushed the United States to drop the ban on Monday, but White House press secretary Jen Psaki downplayed the announcement’s timing shortly before Biden’s U.N. visit.

“If we were going to make things much easier for ourselves, we would have done it prior to June, when the president has his first foreign trip, or earlier this summer,” Psaki said.

The travel ban, though a relatively low-profile issue in the United States, had been particularly galling to Europeans, with one British newspaper dubbing it “Kafkaesque.”

“Over the past few months the travel ban went from a minor irritant in the transatlantic relationship to an existential threat to Biden's Europe policy,” said Thomas Wright, director of the Center on the United States and Europe at the Brookings Institution.

The ban on travelers who had been almost anywhere in Europe in the previous 14 days was first imposed by the Trump administration more than 550 days ago. It stayed in place under Biden even as the coronavirus picture improved in Europe and worsened in the United States.

Although exceptions were made for U.S. citizens and permanent residents, along with a small number of visa holders, the strict rules had stopped millions of potential travelers, costing businesses and leading to personal disruption for Europeans, many of whom missed major life events, including births and deaths.

In total, the travel restrictions affected 33 nations, including Britain, India and China. Munoz, the White House spokesman, said the administration “will continue to assess appropriate protocols” for modes of transportation besides air travel, including those arriving via train or boat.

U.S. airlines and unions supported the move. Nicholas E. Calio, CEO of Airlines for America, a trade group of major carriers, said that “we applaud the administration.” Sara Nelson, international president of the Association of Flight Attendants-CWA, said the announcement “increases our health and safety.”

The most vocal reaction was from Europe, which accounts for a large portion of visitors to the United States.

“Travel ban lifted!” tweeted Stavros Lambrinidis, the European Union’s ambassador to Washington, who only hours earlier had said that E.U. member states had been “working diligently” to help get the ban lifted.

Many on the continent had expected the United States to lift the restrictions over summer, in return for their own relaxation of restrictions on travelers from the United States in June. But no reciprocal move was forthcoming.

Some diplomats fumed that while the restrictions were once understandable, they had become illogical. In contrast to the limits on foreign travelers, U.S. travelers coming from countries with high infection rates faced few restrictions.

Although the E.U. initially lagged behind in vaccinations, it overtook the United States this summer. As of last week, about 60 percent of the population of the 27-nation bloc was fully vaccinated, compared with 53 percent in the United States.

Monday’s announcement appeared to mark a U-turn in thinking from the Biden administration. Last week, citing the spread of the delta variant, Zients told representatives from the U.S. travel industry that the administration was “maintaining the existing travel restrictions at this point.”

Asked about the timing on Monday, Psaki said that the decision emerged from a working group that included various agencies along with “a range of countries and partners.”

“The older rules were not equitable in our view, and they were a bit confusing,” Psaki said.

Secretary of State Antony Blinken held a long discussion about the travel ban on Friday with Philippe Etienne, the French ambassador to Washington, just before Etienne was ordered to return to Paris due to France’s anger over the U.S.-U.K.-Australia submarine deal, said a senior State Department official familiar with the matter, who spoke on the condition of anonymity to discuss sensitive issues.

Asked if the decision to lift the ban was aimed at restoring relations with Europe, Erica Barks-Ruggles, a State Department official at the Bureau of International Organizations, said the decision was “driven by the science.”

Under the new rules, vaccinated travelers to the United States will have to test negative for the virus within three days before departure. The new policy also requires that airlines collect passenger information, including a phone number and email, to improve contact-tracing efforts.

In February, seven U.S. carriers announced they would collect such information from international travelers coming to the United States, but that it would be up to individuals to voluntarily supply it. Under the new White House policy, international travelers will be required to provide these details.

However the decision came about, many across the Atlantic welcomed it.

British Prime Minister Boris Johnson, who is set to meet Biden at the White House on Tuesday, tweeted that he was “delighted” with the news. British newspapers had reported Monday morning that he planned to press the issue with his U.S. counterpart.

The prime minister said it was a “fantastic boost for business and trade, and great that family and friends on both sides of the pond can be reunited once again.”

Ylva Johansson, the E.U.’s commissioner for home affairs, said she “welcomes” the decision. Margaritis Schinas, another high-ranking E.U. official, called the new policy “sound and long-awaited.”

“When I met my U.S. counterparts in July in Lisbon, I told them that mobility cannot be reserved for the elite alone,” he wrote on Twitter. “People need to travel not only officials. Europe the most vaccinated continent in the world.”

John Hudson and Lori Aratani contributed to this report.