SAN DIEGO (AP) — The United States and Mexico are working on plans to halt much of cross-border travel without disrupting trade during the coronavirus outbreak, officials said Thursday.

Mexican Foreign Relations Secretary Marcelo Ebrard said he proposed steps to U.S. Secretary of State Mike Pompeo that “won't paralyze economic activity and keep the border open to commerce and work.” He promised details on Friday.

Pompeo said on Twitter that he was working closely with his Mexican counterpart “on travel restrictions that balance protecting our citizens from further transmission of #COVID19. Together, we can reduce public health risks and prioritize essential cross-border commerce and trade.”

U.S. Customs and Border Protection officials briefed business leaders Thursday on plans to prohibit non-essential travel, similar to a measure announced earlier this week on the Canadian border, said Paola Avila, chair of the Border Trade Alliance, an business group.

The measure would effectively close the U.S. to all tourist and recreational visits along the Mexican border, said Avila, who participated in a conference call with CBP officials. Administration officials said the U.S. would announce it as early as Friday, though details were still being worked out and subject to change, she said.

U.S. officials provided a long list of “essential” workers that would be unaffected going to and from their jobs, including farmworkers, restaurant and grocery store employees and bus drivers, said Avila. Mexico was preparing similar restrictions on visitors from the United States.

U.S. Homeland Security Department officials didn't immediately respond to a request for comment late Thursday.

Keeping trade flowing, as the U.S. and Canada agreed to do, contains the economic damage. Mexico is the U.S.'s largest trading partner, just ahead of Canada. The U.S. accounts for about 75% of Mexican exports, including autos, computers and medical devices.

While halting travel for students, shoppers, families and many workers would be a major blow to border economies, the impact has already been felt.

The State Department on Thursday issued a new travel alert urging Americans not to go abroad under any circumstances and to return home if they are already abroad unless they plan to remain overseas. California Gov. Gavin Newsom ordered the state's 40 million residents to stay at home, restricting non-essential movements.

“It's really not huge,” said Avila, who is also the San Diego Regional Chamber of Commerce vice president for international business affairs. “People are not crossing anyway. This is the right thing to do. If you don’t have to cross, don’t.”

The U.S. has also been considering whether to immediately turn back to Mexico anyone who crosses the border illegally, including asylum-seekers. President Donald Trump said Wednesday that he planned to announce such a measure “very soon,” relying on a law that says he can deny entry to people or reject cargo if the U.S. surgeon general determines there is a "serious danger" of bringing a communicable disease to the United States.