U.S. officials are pressuring airline executives to turn over the email addresses and phone numbers of international passengers as the Trump administration tries to track who may have been exposed to the coronavirus, according to five people briefed on the situation.

Government officials have said they need the data so they can warn local authorities about who might have been exposed to the virus. But the airline industry has balked, saying the federal government should instead share information it already collects among different agencies and come up with a system for obtaining the rest.

The impasse has dragged on for weeks despite concerns about the growing number of people with coronavirus in the United States. It has become a top issue of the Trump administration’s virus task force and U.S. lawmakers. Airline executives are slated to meet with Vice President Pence on Wednesday.

The airline industry has pushed Congress to intervene, with some lobbyists asking lawmakers to insert a provision in an emergency spending package that would effectively absolve the airlines of having to track some of the data.

A failure to resolve the issue could complicate the government’s efforts to contain the outbreak’s spread. United Airlines, Delta Air Lines and American Airlines deferred questions to Airlines for America, a lobbying group that represents the airline industry. Airlines for America said collecting the data shouldn’t be the airlines’ job since the government already has much of it in existing databases. They also said it would take as long as a year for the airlines to set up a tracking system.

The battle over the data has taken on new urgency in recent days.

The Centers for Disease Control and Prevention is asking airlines to collect and — when ordered — submit data from passengers on select international flights within 24 hours in an electronic format. That data might include an email, a phone number and an address in the United States. In the event a passenger on a flight develops covid-19, the disease caused by the coronavirus, that information would enable health officials to reach others who may have been exposed, a system known as “contact tracing.” On Feb. 7, the Department of Health and Human Services issued an interim rule requiring certain passenger data to be shared with federal officials.

“Contact tracing is effective at reducing cases of communicable disease at the early stages of a potential outbreak if the contacts are notified as soon after initial exposure as possible,” the CDC said when it announced the Feb. 7 policy. “If an efficient contact system is not in place when the first ill passengers arrive, the benefits of the contact tracing are greatly diminished.”

The CDC has growing concerns about getting the information it needs for its contact tracing program, saying that under current regulations, it can take nearly two weeks to obtain the traveler data. Even then, some of the information is incomplete.

The passenger data issue has raised alarms at meetings of the U.S. coronavirus task force, according to an official at the Department of Health and Human Services, who spoke on the condition of anonymity to talk candidly about internal meetings. Ken Cuccinelli, acting deputy secretary of homeland security, also flagged the issue during internal administration meetings Saturday, according to another official familiar with the discussions.

Officials say there is greater urgency given the Trump administration’s new travel restrictions affecting Iran, Italy and South Korea. With cases emerging in recent days in Washington state, Oregon, Rhode Island, Florida and New York, the federal government and the airline industry face enormous pressure to put in place a tracking system amid fears of the coronavirus’s spread.

“When the goal is containment, timing is of the essence,” said Josh Michaud, associate director for global health policy at the Kaiser Family Foundation. “The earlier you are able to find these people, get them into testing and, if needed, quarantine, the more likely you are to prevent future spreading.”

In the three weeks since HHS’s rule was put into effect, airlines have turned over some information, but it has been “incomplete,” according to the HHS official. U.S. officials want to know who was traveling on planes that were later determined to be transporting passengers who had the coronavirus. For example, if a passenger on a flight from Italy two weeks ago tested positive for the virus last week, CDC officials want to track down fellow passengers on that flight to monitor their health and determine who else might have been exposed.

Right now, when a plane from China lands in the United States, U.S. citizens who are not sick and not showing symptoms are given instructions at the airport to monitor themselves for symptoms, such as fever, cough or difficulty breathing. After they reach their final destination, they are supposed to stay home and monitor their health for 14 days from the time they left China. If they develop symptoms, they are supposed to contact their health-care providers and their local public health authorities.

The CDC wants passenger data from the airlines so the agency can pass it on to states and counties, allowing those front-line authorities to “call in and check in on” those individuals to make sure they are not sick, the official said. CDC officials regard this basic information as critical to efforts to control the spread of the virus.

The airlines have been warning the government at least since the beginning of February that they lack the capacity to quickly set up a tracking system, said Nicholas E. Calio, CEO of Airlines for America. Creating the system could take a year or longer, Calio said, and airlines often do not have the necessary passenger information available to them if flights were booked with a third party.

Most of the airlines’ current systems would have to be reprogrammed to collect additional data, and the airlines contend that they have no way of verifying that the information they receive is accurate.

“We have some of the information, but we don’t have all of it,” said Sharon Pinkerton, senior vice president for legislative and regulatory policy at Airlines for America.

In a letter to HHS, Calio wrote that roughly 74 percent of all passengers list a phone number and 56 percent list an email address in the “passenger name record,” a type of government database that tracks travelers. Calio also said that the airline industry was willing to work with the federal government to address any gaps.

Airline companies have asked Congress to require HHS to create a portal that sends passenger information to the CDC, according to a memo sent by industry lobbyists to lawmakers and described to The Washington Post.

Such a legislative measure would effectively absolve the airlines of having to track and send the information to the CDC, but it is unlikely to be approved when Congress takes up the broader emergency package this week, according to two congressional aides who spoke on the condition of anonymity to describe fast-moving negotiations. Calio said the airlines are willing to pay to develop an online database in which travelers directly provide their information to the CDC.

Lawmakers are hoping to resolve the impasse quickly. In addition to the meeting between airline executives and Pence, airline lobbyists are also expected to meet this week with members of the Senate Committee on Commerce, Science and Transportation, including Sen. Ted Cruz (R-Tex.), who chairs the panel’s subcommittee on aviation and space.