Democratic presidential candidate Sen. Bernie Sanders Sanders said that he would be campaigning in the western half of the country and unable to attend the AIPAC conference. (Ralph Freso/AP)

Democratic presidential candidate Bernie Sanders has notified AIPAC that he will not attend its annual conference next week, the only presidential hopeful from either party to be a no-show.

In a letter sent Friday to Roger Cohen, president of the prominent American Israel Public Affairs Committee, Sanders said that he would be campaigning in the western half of the country, and that “the campaign schedule that we have prevents me from attending.”

His Democratic primary opponent, Hillary Clinton, is scheduled to address the group Monday. The three remaining Republican candidates — businessman Donald Trump, Sen. Ted Cruz (Tex.) and Ohio Gov. John Kasich — are slated to speak later in the day.

Sanders expressed regret, saying he would have enjoyed the chance to speak at AIPAC.

“Obviously, issues impacting Israel and the Middle East are of the utmost importance to me, to our country and to the world,” he wrote to Cohen.

Sanders offered to send a copy of the speech he would have made had he attended, citing AIPAC’s decision not to allow candidates to address the conference remotely, and ended on a breezy note: “Thanks very much. Hope the conference goes well.”

AIPAC’s annual convention attracts an A-list array of politicians. Vice President Biden was scheduled to speak at the opening of the multi-day conference, and House Speaker Paul D. Ryan (R-Wis.) was to appear alongside the GOP candidates.

Israeli Prime Minister Benjamin Netanyahu, who also canceled an appearance before AIPAC and a meeting with President Obama, is expected to appear live via satellite.