Former Vice President Joe Biden Joe BidenBiden says voters should choose who nominates Supreme Court justice Trump, Biden will not shake hands at first debate due to COVID-19 Joe Biden should enact critical government reforms if he wins MORE on Monday hit President Trump Donald John TrumpBiden says voters should choose who nominates Supreme Court justice Trump, Biden will not shake hands at first debate due to COVID-19 Pelosi: Trump Supreme Court pick 'threatens' Affordable Care Act MORE on foreign policy ahead of this week's NATO summit, accusing the president of abdicating U.S. leadership.

"His abdication of America’s traditional leadership role could not come at a more critical moment for the alliance," Biden said in a statement, citing Russia's aggressive stances against U.S. allies in Europe, as well as meddling in "the democratic processes" of NATO members.

"The failure of American leadership and rising authoritarianism, even among some NATO members, threaten these critical pillars of NATO," the former vice president continued.

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This is not the first time Biden has hit Trump over his policies on NATO.

The former vice president said in an interview with CNN earlier this year that the alliance would cease to exist if Trump is reelected in 2020.

Biden has capitalized on his foreign policy experience throughout the presidential campaign, citing his work in the Obama administration, as well as serving as chairman of the Senate Foreign Relations Committee.

Trump will head to London this week to meet with other NATO leaders and members as the alliance turns 70 years old.

The president has long questioned the alliance's purpose and has argued that the U.S. contributes a disproportionate amount of financial aid to the group, compared to the 28 other member nations.

Trump has said that his tough rhetoric toward the alliance has resulted in positive concessions for the U.S. in the group.