One of Joe Bidens strongest pitches to voters as he seeks the presidency is his breadth of foreign policy experience, from his time as chairman of the Senate Foreign Relations Committee to his extensive diplomacy as vice president.

But a new letter thats being circulated among delegates to the Democratic National Convention is raising alarm bells about the circle of advisers who would likely form Bidens foreign policy team if he becomes president. A widely circulated message promoting the letter, which is already signed by more than 275 delegates almost all of whom were pledged to Sen. Bernie Sanders (I-Vt.) says Bidens current circle is a horror show of advisers with track records of supporting disastrous U.S. military interventions.

The letter, obtained by HuffPost, attacks the poor judgment of former Ambassador to the United Nations Susan Rice, whos rumored to be on Bidens short list of vice presidential candidates, and Antony Blinken, Bidens long-time chief aide on foreign affairs, as well as several other prominent advisers who would likely be in line for cabinet-level appointments in a Biden administration.

We ask you not to rely on foreign policy advice from those who may have a conflict of interest as a result of their relationships and lobbying on behalf of merchants selling weapons and surveillance technology, the letter says. We ask you to appoint top foreign policy advisors whose records reflect good judgment and an understanding of the importance of diplomacy and international cooperation, particularly in the face of global climate catastrophe.

The message notes that Blinken co-founded a company called WestExec Advisors , which was involved in a Pentagon effort to enhance drone warfare , and that another Biden advisor, former Defense Department official Michle Flournoy, worked at Boston Consulting Group for years, during which the firm increased its contracts with the military by many millions of dollars.

It also highlights Avril Haines, a former CIA deputy director who is unpopular on the left for her role in redacting a report on President George W. Bushs use of torture and her role in President Barack Obamas program of targeted killing; former Obama aides Samantha Power and Jake Sullivan, who supported the presidents intervention in Libyas civil war; Nicholas Burns, a former diplomat in the running for secretary of state, for supporting the invasion of Iraq and condemning whistleblower Edward Snowden; and Amit Jani, who runs Asian American outreach for Biden and has links to right-wing Indian Prime Minister Narendra Modi.

The organizers of the letter are hoping to gather more signatures from delegates before August 17, the start of the convention at which Biden will be formally nominated. So far its signatories include roughly a third of those delegates pledged to Sanders.

The effort is unlikely to force the former vice president to change his national security staff, most of whom he has worked with and respected for some time. But it shows he will continue to face pressure from some liberals who want a less hawkish foreign policy under a future Democratic president.

Progressives want to see a strong commitment from the Biden team on advancing a more principled foreign policy that prioritizes diplomacy and multilateralism, but also a level of assurance that those advising Vice President Biden on foreign policy have a consistent record of opposing regime-change interventions, rejecting the whitewashing of torture, and opposing arming authoritarian governments engaging in systematic human rights violations, said Yasmine Taeb, senior policy counsel at the advocacy group Demand Progress.

Sanders was Bidens chief rival in the Democratic presidential primary and emphasized a more progressive foreign policy in his pitch to voters, often citing Americas past mistakes abroad. After he dropped out, Biden and Sanders developed joint task forces to craft policies on a range of issues in order to reflect the diversity of views within the party. Notably, they did not form a task force on national security.

A Sanders aide declined to comment on the letter.

Bidens team has signaled that it is open to hearing from left-wing voices on foreign policy, regularly reaching out to grassroots activists who have rallied Democratic campaigners and lawmakers against policies like U.S. support for the Saudi-led coalition in Yemen, and unquestioned American assistance to Israel despite its suppression of Palestinians. But Bidens camp has also been wary of pledging big changes or of making choices that could be perceived as controversial a tendency that most recently caused an intra-party split on whether to call Israels control of territory integral to a future Palestinian state an occupation in the Democrats 2020 platform. Biden staffers left out the term over objections from Sanders supporters and it is unlikely to be used in the platform, which is currently being finalized.

The Biden campaign did not immediately respond to a request for comment, but later on Wednesday, former Biden aide Jon Wolfsthal indicated that the candidates circle has deep faith in the figures the delegates are hoping to remove.

Rice, Blinken and Haines are perhaps the smartest, most dedicated and principled people I have ever met, Wolfsthal, who is now with the anti-nuclear weapons group Global Zero, wrote on Twitter . I would trust no one to more honestly and doggedly guide American foreign policy. Should they have the chance to serve, we will all be better off.