OTTAWA -- Millions of visitors to Canada will pay a $7 application fee beginning next April under a new electronic security screening plan.

The federal government announced the fee Friday for online travel applications, a key element of the perimeter pact with the United States intended to protect the continent from security threats.

Foreign nationals who currently do not need a visa to visit Canada -- including people from Britain, France and many other countries -- would have to successfully apply for a so-called electronic travel authorization before arriving by air.

U.S. citizens would be exempted from the requirement.

Visitors would apply through the Citizenship and Immigration website by entering biographic details, passport and background information -- the kind of data now requested by officers at Canadian entry ports or in a visa application.

Officials would verify the information against immigration and enforcement databases and conduct a risk assessment of the applicant.

Canada expects approximately 3.5 million electronic travel authorization applications annually.

"The information required by these proposed amendments would allow Canada to determine the admissibility of foreign nationals before they arrive at the border and whether their travel poses migration or security risks," says the federal notice published Friday.

In 2012--2013, more than 7,000 visa-exempt foreign nationals were found ineligible to enter Canada for various reasons upon arriving in Canada by air, the government says. That includes 28 people who had previously been handed removal orders and were trying to return to Canada without authorization.

Reasons for refusing entry can include membership in terrorist or organized crime groups, espionage, participation in war crimes, human rights violations or endangerment of public health due to tuberculosis or other conditions.

"At present, the government of Canada does not possess the necessary authority to screen these individuals before they travel to Canada," the federal notice says. "This causes significant expense, delay and inconvenience for the inadmissible foreign national, other travellers, airlines and the Canadian government."

Under the new system, unwelcome travellers would be advised before getting on a plane to Canada.

All negative decisions would be made by an officer following a thorough review, the notice says.

Highly complex cases -- expected to be "very few" in number -- would require assessment by a senior decision-maker and could be referred to an overseas Canadian mission, it adds.

"Once a case is referred overseas, applicants may be asked to provide documentation to support their application, as well as to attend an interview with an officer to confirm that they are a bona fide traveller."

Some cases may also require further investigation by the Canadian border agency, the Canadian Security Intelligence Service or the RCMP.

The $7 fee is intended to cover processing costs for each travel authorization, which would be valid for five years from date of issue or until the applicant's passport or travel document expires.

During consultations, some expressed concern that the fee would discourage tourism.

However, the notice says, the price is competitive with similar systems in place elsewhere including the U.S. and Australia.

Successful introduction of the electronic travel authorization could persuade the federal government to allow visitors from countries such as Mexico, Brazil and Chile -- who now require a visa to come to Canada -- to use the new, less onerous document, said David Goldstein, president of the Tourism Industry Association of Canada.

"That's the direction we've been presenting to the government."