Premier Doug Ford is once again pleading with the federal government to tighten border restrictions to help stop the spread of COVID-19. And this time, he is warning of a fourth wave.

The premier's office released a statement on Tuesday, saying that the provincial government has tried multiple times to appeal to the federal government on the issue, but has received no "formal response."

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The letter outlines the danger of keeping Toronto Pearson International Airport open as flights with confirmed cases of COVID-19 continue to land in the province. It also calls on the federal government to ban all non-essential travel.

"We are once again pleading with the federal government to impose stricter measures at our borders, including banning all non-essential travel, implementing pre-departure PCR testing for domestic flights and closing the quarantine loophole at land border crossings," the statement reads.

"More can and must be done. We cannot sit back and watch the fourth wave of COVID-19 walk across our border," it said.