Story highlights The trip comes four days before NY votes

Sanders' announcement makes no mention of meeting the Pope

(CNN) Bernie Sanders' campaign announced Friday that the Vermont senator will visit Vatican City on April 15 -- just four days before the crucial New York primary.

Sanders was invited to attend a conference hosted by the Pontifical Academy of Social Sciences "on social, economic, and environmental issues," according to a release from the Sanders campaign.

The trip abroad means that Sanders will be off the campaign trail in New York for a period of time before the state's hotly contested April 19 primary against Hillary Clinton. Sanders has been hoping to upset Clinton in her home state and his absence from the campaign trail in the final week of the battle for New York comes as a surprise.

The Democratic presidential candidate's appearance at the conference will coincide with the 25th anniversary of the "Centesimus Annus," an encyclical from Pope John Paul II that addresses workers' rights and other economic and social issues that are similar to those Sanders has stressed in his White House bid.

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