HAVANA, Cuba (AP) — The Cuban government announced Tuesday that it is reimposing a hated travel permit requirement on many doctors, requiring them to get permission to leave the country in an attempt to counter a brain drain that it blames on the United States.

It is the first major reverse in Cuba’s policy of allowing unrestricted travel for its citizens, put in place in 2013 as President Raul Castro allowed new freedoms as part of a broad set of social and economic reforms.

The government announced on the front page of state media that health professionals in specialties that have been drained by large-scale emigration in recent years will now be required to get permission from Health Ministry officials in order to leave the country.

The new policy was announced hours after the end of a meeting Monday between US and Cuban negotiators in Washington to address a crisis in Cuban migration, which has reached its highest levels in at least two decades. Cuba complained that the US said it had no plans to change Cold War-era policies that give automatic legal residency to Cuban immigrants.

Many Cuban doctors cite low pay, poor working conditions and the possibility of well-compensated jobs in other countries as their primary reasons for emigrating. The Cuban government places the blame on the U.S. policy of granting automatic legal residency to Cuban immigrants, with special fast-track benefits for doctors who abandon government medical missions overseas.

The government announcement cited anaesthesiology, neurosurgery, obstetrics and gynaecology and neonatal care as among the specialities worst-hit by emigration of doctors in recent years.

“The migration of Cuban health professionals is a concern for the country,” the government announcement read, blaming US laws that aid Cuban medical emigration for having “the perverse objective of pushing Cuban health professionals to abandon their missions in other countries.”

The Cuban government cites free, universal health care system as one of the crowning achievements of its socialist revolution. Medical missions abroad are one of the most important sources of foreign exchange for the Cuban government, which receives tens of thousands of dollars a year in cash or commodities for each doctor it sends overseas.

Inside Cuba, many doctors and nurses complain that their profession has been devastated by waves of departures, with vital specialists now absent in many clinics and hospitals.

Over the past two years, at least 100,000 Cubans have emigrated to the United States, the majority making a treacherous land journey from Ecuador through South and Central America and Mexico. The pace has quickened dramatically this year, with many Cubans fearing that the detente announced nearly a year ago between the United States and Cuba will mean the end to special migration privileges.

Left-leaning Latin American allies of Cuba began cracking down on Cuban migration last month. Nicaragua closed its border to Cuban migrants, leaving at least 3,000 trapped in emergency shelters in northern Costa Rica. And Ecuador last week imposed a visa requirement for Cuban travellers in an attempt to end its role as the starting point for most Cuban migration.

The Ecuadorean move set off two days of angry protests outside the country’s embassy in Havana, a highly unusual event in a country where the government unleashes swift crackdowns on unauthorized street demonstrations.