Former New Jersey Governor Chris Christie called out President Biden on Monday for allowing Canada to receive COVID-19 vaccines from the U.S. while at the same time barring fully vaccinated Americans from crossing the northern border.

Christie blasted the president in a tweet posted Monday, saying more losing the upper hand coming from the Biden administration’s foreign policy and vaccine messaging with Canada.

"More weakness from Biden foreign policy and mixed messages on vaccines," Christie, a potential 2024 presidential candidate, wrote on Twitter. "Canada continues to ask for US help with vaccines but refuses to allow for fully vaccinated Americans to enter Canada."

US, CANADA, MEXICO NON-ESSENTIAL TRAVEL RESTRICTIONS EXTENDED TO JUNE 21

"This is just wrong," Christie continued. "A double standard where America and Americans are being used."

Christie followed up the tweet with another calling on Biden to "push back" against Canada’s foreign policy and stand up for America.

"President Biden must push back [and] insist that if Canada believes in science [and] wants our vaccines, then they need to accept the broader premise that vaccinated people crossing borders either way go hand in hand with the notion of expanded vaccination success," the New Jersey Republican wrote. "Stand up for America!"

The former governor’s criticism comes after the U.S., Canada and Mexico agreed to extend the coronavirus restrictions on nonessential travel across land borders last week.

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"To fight [COVID-19] spread and protect our citizens, the U.S. is continuing restrictions on non-essential travel at land borders through June 21, while allowing essential trade [and] travel," the Department of Homeland Security wrote on Twitter last week. "We're working closely with Canada [and] Mexico to safely ease restrictions as conditions improve."

The White House did not immediately respond to Fox News' request for comment on Christie's criticisms.