They're our allies and biggest trading partner, separated from us only by the world's longest undefended border, but Canada is warning American travellers it's a good idea to leave their guns at home when they head north.

Despite the quickly approaching end of the summer travel season, the Canada Border Services Agency (CBSA) on Monday launched a firearms awareness campaign to remind U.S. travellers about Canadian gun laws.

"Canadian laws are different than U.S. ones," the CBSA said in a news release about the campaign. "Canadian firearm laws are clear - failure to declare any firearm may lead to seizure action, penalty, prosecution in a court of law; and may make you inadmissible to Canada. Your vehicle may also be seized and you will have to pay a penalty to get it back."

The CBSA suggests travellers check the laws before arriving at the border and strongly recommends Americans not try to bring their guns into Canada, even if they're just passing through on their way to another U.S. destination.

"However, should you choose to travel with your firearms, you must declare all firearms in your possession at the first Canadian designated port of entry," the news release says. "You must also have all the necessary permits and have your firearm appropriately stored."

More than 400,000 people cross the Canada-U.S. border every day as part of a trade relationship worth $670 billion a year. U.S. residents represented 70 per cent of international overnight visitors to Canada in 2014, according to Destination Canada, the Crown corporation responsible for marketing the country to tourists. With 11.5 million Americans visiting Canada that year, that makes the U.S. our largest inbound travel market.

As of last May, U.S. visits to Canada were up 13.3 per cent for the first part of 2016, Destination Canada reported. That's the highest number of American visitors to Canada for that period since 2004, likely due to the American dollar's strength compared to the loonie.

Most firearms seized at the border are from U.S. travellers seeking to enter Canada, CBSA says in its news release.

"Firearms are high-risk commodities and their interdiction is an enforcement priority for Canada," CBSA said.

"We welcome our U.S. neighbours in Canada - to make your journey more pleasant, travel light and always remember to declare all goods with you."

The CBSA provided some recent examples of gun seizures and fines, including: