Hundreds of foreign policy and national security professionals endorsed South Bend Mayor Pete Buttigieg in a letter on Monday.

The letter, which is heavily critical of President Donald Trump's approach to foreign policy, describes Buttigieg as someone with "intelligence, steadiness, demeanor and understanding of the forces now shaping the world."

"This Midwestern native's vision for the future of American global engagement...defines the framework necessary to restore our country's leadership abroad," the letter states.

A number of those who signed the letter are former Obama administration officials.

This poses a direct challenge to former Vice President Joe Biden, who often touts his foreign policy credentials and portrays himself as the candidate with the best chance of restoring America's global credibility.

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South Bend Mayor Pete Buttigieg has been endorsed in a joint letter by over 200 foreign policy and national security professionals, USA Today first reported on Monday.

Among those endorsing Buttigieg are a number of former Obama administration officials, including: former Secretary of the Army Eric Fanning, former deputy CIA director David Cohen, former Assistant Secretary of State Philip Gordon, and former National Security Council spokesman Ned Price.

The letter, which is heavily critical of President Donald Trump's approach to foreign policy, touts Buttigieg as someone with "intelligence, steadiness, demeanor and understanding of the forces now shaping the world." Meanwhile, it decries Trump as a president who "withdraws from treaties, berates our allies and praises authoritarian leaders."

"We believe in America's international leadership, and in the values that underpin its capability to bring about collective security and prosperity, as well as change for the greater good," the letter adds. "So we cannot stand by and continue to watch all that we have stood and worked for tweeted away."

The letter describes Buttigieg as a candidate who over the past year has emerged as a "young leader who shares our belief in America's leadership role and values." It characterizes the South Bend mayor as someone who sees "the big picture and plays the long game," portraying these as "essential traits for implementing consistent and effective national security and foreign policies."

"This Midwestern native's vision for the future of American global engagement...defines the framework necessary to restore our country's leadership abroad," the letter goes on to say.

Buttigieg, 37, a former Navy intelligence officer who served in Afghanistan, has risen to the top of the polls in important early voting states like Iowa and New Hampshire in recent weeks. He's generally placed in fourth place overall in national polls, with former Vice President Joe Biden in first, and Sens. Bernie Sanders and Elizabeth Warren jockeying for second.

Biden has emphasized his foreign policy credentials along the campaign trail, presenting himself as someone who could rehabilitate the country's global image post-Trump. But this new letter from a huge number of foreign policy and national security professionals endorsing Buttigieg could pose a challenge to the former vice president.

The South Bend mayor has often leaned on his experience in Afghanistan in discussing foreign policy along the campaign trail.

In an interview with Washington Post's editorial board earlier this month, Buttigieg said: "I thought, I was made to feel like I was one of the very last troops turning out the lights when we were packing up and leaving. And years later, we're still there in comparable proportion. So that's clearly got to come to an end."