MONTREAL (Reuters) -Air Canada is seeing a "low teens" percentage decline in bookings over the next six months for trips across the U.S. border amid trade tensions and a weaker Canadian dollar, the airline's CEO said on Friday.

Canada's largest carrier on Thursday lowered its annual adjusted core profit forecast and posted first-quarter revenue below analysts' estimates on softer trans-border traffic.

Air Canada previously said its decline in U.S.-bound bookings over the next six months mirrored an industry-wide drop of roughly 10%.

"Uncertainty was for sure the main theme during the first quarter," CEO Mike Rousseau told analysts.

"We are experiencing booking declines on the trans-border market in the low teens on average over the next six months."

Canadians are boycotting U.S.-made goods and cancelling trips south of the border after President Donald Trump's tariffs and his suggestions that Canada should be annexed by the United States.

Overall, booking trends remain stable, given Air Canada's diverse network and exposure to international destinations, where demand remains strong. Results were solid in Mexico and the Caribbean as Canadians look for alternative destinations, the carrier said.

North American carriers have been trimming flight schedules amid weakening U.S. domestic bookings, scrapping financial forecasts and tightening cost controls - including on rising labor expenses - to safeguard margins.