TORONTO -- The Ontario government says that international travellers will have to undergo mandatory COVID-19 testing at the province's largest airport as of Monday, weeks before the federal government is expected to implement its own policy Canada-wide.

Ontario Premier Doug Ford made the announcement Friday afternoon at Queen’s Park alongside Health Minister Christine Elliott and Solicitor General Sylvia Jones.

“We can’t take anything for granted, not when new highly contagious strains of the virus have entered our country,” Ford said.

The new testing rules will go into effect at Toronto Pearson International Airport at noon on Monday. Those who refuse will receive a $750 fine under the Health Protection and Promotion Act, the province said.

“I don't anticipate the vast majority of travellers will refuse that test.” Jones said. “I am hopeful that when they are guests in our country in Ontario, that they understand we are only doing this to keep our citizens safe, and that they would voluntarily comply and take that test at the airport.”

The Ontario government has been calling on the federal government to implement the measure, namely at Pearson International Airport, in recent weeks as more cases of variants are reported by the province.

Friday's mandatory testing measures came hours after Prime Minister Justin Trudeau announced that all Canadian travellers returning from overseas will have to take a COVID-19 PCR test at the airport, and quarantine in a designated hotel for three days at their own expense while they await results.

Those with negative test results will be able to then isolate at home for the remainder of the 14 days, while those with positive tests will be immediately required to quarantine in designated government facilities.

However, the federal government indicated that it could take a few weeks before the policy goes into effect. The premier said that Ontario’s mandatory testing rules will “serve as a stopgap” until the federal regulations are in place.

“I welcome the new measures announced by the federal government today,” Ford said. “We've been calling for stronger measures at the border for months.”

"However, it looks like these new measures won't be fully in place until a few weeks from now. That's a few weeks too long. That's why today, our government is taking swift and decisive action. We're releasing a six-point plan to stop the spread of COVID-19 variants.”

In addition to mandatory COVID-19 tests, the province also wants to explore “additional testing measures” at land border crossings in the coming weeks.

Officials said that provincial diagnostic labs are ramping up capacity to screen positive tests for a variant within two to three days, with the goal of undergoing full genomic sequencing on 10 per cent of samples by mid-February.

Since early January, international travellers have been given the choice to take a COVID-19 test upon arrival through a provincial pilot program launched earlier this month. Of the nearly 7,000 people who took a test, about 2.6 per cent of the samples came back positive.

On Friday, Ford said that five cases of a COVID-19 variant were discovered using this pilot program.

“These are five cases that could have otherwise gone unnoticed, five cases that could have infected others,” he said.

In new COVID-19 modelling released Thursday, Ontario health officials suggested that the highly contagious U.K. variant will likely be the dominant strain in the province by March.

"The new variants give us less room to relax and less room for error,” Dr. Adalsteinn Brown, co-chair of the province's COVID-19 science table, said at the time.

The advisory table went on to say that current evidence shows that the U.K. variant, also known as VOC B.1.1.7, may be associated with an “increased risk of death” compared to infection with non-VOC viruses.

And while Brown said that the COVID-19 vaccines will likely still be effective against the U.K. strain of the disease he added, “it’s important to note that these are not the only variants that will emerge as the disease continues to spread."

At least 51 cases of the variant have been recorded in Ontario so far.

With files from CTV News Toronto's Phil Tsekouras