Mayor Bill de Blasio is Italy-bound for the second summer in a row.
The mayor, who has traveled extensively across Europe and the United States during his 18 months in office, is set to fly to Rome next week to address an international gathering of mayors and environmental leaders at the Vatican.
The meeting on Tuesday, titled “Modern Slavery and Climate Change,” is an outgrowth of a papal encyclical issued last month that called on world leaders to embark on a more aggressive defense of the environment.
Pope Francis, ahead of a visit to the United States this fall, is expected to address the event’s attendees, including Gov. Jerry Brown of California and about 60 other officials. The mayor plans to deliver a speech describing his administration’s environmental plan for New York, known as OneNYC.
This will be Mr. de Blasio’s fourth European excursion since taking office in 2014. He and his family took an extended vacation in Italy last summer, and the mayor has traveled to Paris and Cambridge, England. His wife, Chirlane McCray, went to Florence this spring to speak at a cultural conference sponsored by New York University.
Airfare, lodging and expenses for the Vatican trip will be paid by the city, according to mayoral aides, who confirmed the trip after an inquiry on Wednesday. Mr. de Blasio, who will be accompanied by two staff members and his police detail, is due back in New York on Wednesday evening.
Mr. de Blasio, who does not belong to a church, has been outspoken in his admiration of Francis, a relatively liberal pontiff. The mayor has also made clear he is enchanted by Italy, the birthplace of his maternal ancestors.
“Pope Francis has been one of the world’s most powerful voices on fighting income inequality, and Mayor de Blasio shares the pope’s belief that addressing climate change is essential to that fight,” Monica Klein, a City Hall spokeswoman, said in a statement.
Jeffrey D. Sachs, a Columbia economist and a longtime supporter of Mr. de Blasio’s, helped organize the Vatican conference. He said on Wednesday that Francis was “extremely excited about Mayor de Blasio coming.”
“I’m thrilled that the mayor will present OneNYC, and the challenges and the approaches of New York City, to dozens of other mayors around the world,” Mr. Sachs added, speaking via Skype from Addis Ababa, Ethiopia, where he is attending a development conference. “It’s really going to have a galvanizing effect.”
Mr. de Blasio, a Democrat, relishes travel, although his journeys have not been without controversy. Recently, he faced some backlash after a rapid-fire series of trips to California, Iowa, Nebraska, Wisconsin and Washington D.C., a tour intended to jump-start a national liberal movement.
He is also the first New York mayor since David N. Dinkins to take vacations of more than a few days while in office. He arrived back in the city last week after an eight-day family trip that spanned the Fourth of July weekend, including stops in Arizona, California and New Mexico.
Still, few New York mayors have been shy about traveling internationally for work. Michael R. Bloomberg, for instance, flew to events across Europe and Asia. (He also spent many weekends at a home in Bermuda.)
The Vatican trip is almost certainly not Mr. de Blasio’s last one abroad.
He had previously pledged to visit Israel this summer, to “stand in solidarity” against anti-Jewish violence. On Wednesday, his aides said that they were still working out a date.