VATICAN CITY (AP) — Mayors emboldened by an appeal from Pope Francis committed themselves Wednesday to a new set of U.N. goals to end poverty and promote sustainable development over the next 15 years.

At the end of a two-day Vatican summit, several dozen mayors from around the world unanimously adopted a declaration pledging to endorse the goals and work to implement them in their home cities.

World leaders are set to adopt the 17 "sustainable development goals" at a U.N. summit in September that will be opened by Francis. Among other things, the goals commit leaders to end extreme poverty and hunger by 2030, ensure health care, education, access to water, sustainable energy and growth for all — and take urgent action to combat climate change and protect the Earth.

The Vatican invited some 60 mayors (from as far away as Porto Alegre, Brazil and Bojonegoro, Indonesia) to commit to fighting climate change, well aware that cities are key to tackling global warming. Cities account for two-thirds of the world's greenhouse-gas emissions, are the drivers of the world economy and are expected to grow enormously over the coming decades as the poor flock to urban centers in search of work.

At the opening of the summit Tuesday, Francis told the leaders that their commitments were paramount to sensitizing the "conscience of humanity" about the intrinsic link between caring for the planet and its most vulnerable people.

The aim of the two-day meeting was to put pressure on national leaders to make solid commitments at the September U.N. development summit as well as climate negotiations in Paris later this year. Experts say the Paris talks are critical to negotiating targets that will keep global temperatures from rising more than 2 degrees Celsius compared to pre-industrial times.

Conservatives have criticized the Vatican for cozying up to the U.N. on the sustainable development agenda since some of the goals include ensuring reproductive health care for girls, which means access to contraception and abortion.

To that criticism, the head of the Pontifical Academy of Sciences, Monsignor Marcelo Sanchez Sorondo, responded: "The United Nations is not the devil! Rather quite the opposite."