Six international airlines have suspended flights to Venezuela following a United States warning to major carriers about a “potentially hazardous situation” amid “heightened military activity” in the region.

The affected airlines, Spain’s Iberia, Portugal’s TAP, Chile’s LATAM, Colombia’s Avianca, Brazil’s GOL, and Trinidad and Tobago’s Caribbean, halted operations on Saturday, according to AFP, citing Marisela de Loaiza, president of the Venezuelan Airlines Association.

TAP announced it would cancel flights scheduled for Saturday and next Tuesday, while Iberia said it was suspending flights to Caracas until further notice.

It is reported that Panama’s Copa Airlines, Spain’s Air Europa and PlusUltra, Turkish Airlines, and Venezuela’s LASER are continuing to operate flights for now.

Flight suspensions coincide with escalating tensions between the U.S. and Venezuela, as Washington sends troops and the world’s largest aircraft carrier to the Caribbean in what it calls an anti-narcotics mission.

Caracas, however, claims the operation is aimed at forcing Venezuelan President Nicolás Maduro from power.

The U.S. military has reportedly carried out at least 21 strikes on suspected drug vessels in the Caribbean and Pacific, killing at least 83 people.

Maduro has accused the US of creating “pretexts” for conflict, reiterating his openness to dialogue with Washington while cautioning that Venezuela will defend itself if necessary.

“No foreign power will impose its will on our sovereign homeland,” he was quoted as saying by the Venezuelan outlet Telesur.

“But if they break peace and persist in their neocolonial intentions, they will face a huge surprise. I pray that does not occur, because – I repeat – they will receive a truly monumental surprise.”