Democratic US presidential candidates Amy Klobuchar and Pete Buttigieg announced this week that they will not attend the annual America Israel Public Affairs Committee (AIPAC) conference next week.

They join presidential hopefuls Bernie Sanders and Elizabeth Warren, who have also said they will skip the annual meeting in Washington, DC.

Officials from the Buttigieg and Klobuchar campaigns said the conference, normally attended by a bipartisan array of US political figures, overlaps too closely with the critical Super Tuesday primary on March 3. This year's AIPAC event will be held from March 1-3 in Washington, DC.

More:

The AIPAC event is an annual gathering of pro-Israel leaders and personalities intended to highlight ways to strengthen US-Israeli ties and show support for the state of Israel. For years, it has been a must-attend for aspiring politicians from both the Republican and Democratic parties.

The progressive wing of the Democratic slate, Sanders and Elizabeth, earlier said they would skip the conference amid liberal concerns about AIPAC's unwavering alignment with the conservative Israeli government. Sanders tweeted during the weekend that he is "concerned about the platform AIPAC provides for leaders who express bigotry and oppose basic Palestinian rights."

The Israeli people have the right to live in peace and security. So do the Palestinian people. I remain concerned about the platform AIPAC provides for leaders who express bigotry and oppose basic Palestinian rights. For that reason I will not attend their conference. 1/2 — Bernie Sanders (@BernieSanders) February 23, 2020

In response, a group of 300 US rabbis called Sanders's comments "outrageous" in an open letter to the Vermont senator. "AIPAC is one of the last remaining vehicles in American politics that proactively seeks to bring Americans from across the political spectrum together to achieve a common goal," the letter stated.

Pressure not to attend came from liberal advocacy groups such as MoveOn and IfNotNow, who accuse organisers of the event of employing "anti-Muslim and anti-Arab rhetoric". By not attending, the groups said, the Democratic candidates can demonstrate their progressive bona fides.

In a tweet on Thursday, IfNotNow praised the candidates' decision as a "historic moment".

"In recent memory, there hasn't been an election year with the majority of Democratic presidential candidates skipping the AIPAC conference," the group said. "Until now."

Earlier this week, activists protested outside of former Vice President Joe Biden's Philadelphia, Pennsylvania, campaign offices to demand he, too, skip the conference. Biden has previously rejected calls to boycott the meeting, saying he would be there to "convince them to change their position". His campaign has not publicly confirmed his attendance.

Billionaire Michael Bloomberg is the sole Democratic presidential hopeful scheduled to address this year's conference.

A number of prominent Democrats, however, are still on the schedule, among them Senate Majority Leader Chuck Schumer and Congressman Hakeem Jeffries, chair of the House Democratic Caucus and one of the House managers in the impeachment trial of President Donald Trump. A number of Republicans will also be attending, including Vice President Mike Pence and Secretary of State Mike Pompeo.

Last year's AIPAC conference also got the cold shoulder from Democratic candidates. Warren, Sanders, former Texas Congressman Beto O'Rourke, and senators Kamala Harris and Kirsten Gillibrand all skipped the 2019 gathering.