Pope Francis called Wednesday for urgent efforts to tackle climate change, calling it a problem that shouldn't be passed onto future generations, as he delivered his first address on a landmark visit to the United States.

"I find it encouraging that you are proposing an initiative for reducing air pollution," the pope said at a welcoming ceremony at the White House before talks with President Barack Obama.

"Accepting the urgency, it seems clear to me also that climate change is a problem which can no longer be left to our future generation."

"When it comes to the care of our common home, we are living at a critical moment of history. We still have time to make the change needed to bring about a sustainable and integral development, for we know that things can change," he said.

Climate change is one of the pope's top priorities and Obama also sees the fight against climate change as one of his legacy projects. However, it is one of sensitive political issues in the U.S., with the Republican Party opposing Obama's initiative for hurting the economy.

"Holy Father, you remind us that we have a sacred obligation to protect our planet, God's magnificent gift to us," Obama said. "We support your call to all world leaders to support the communities most vulnerable to changing climate, and to come together to preserve our precious world for future generations."

During the speech, the pope also touched on immigration, another sensitive political issue ahead of next year's presidential election, describing himself as a "son of an immigrant family" and saying the U.S. "was largely built by such families."

The pope arrived in Washington on Tuesday on his first-ever trip to the U.S.

On Thursday, he is scheduled to address a joint meeting of the House and the Senate, which will mark the first-ever speech by a pope before Congress. The address will also be watched closely as he is expected to speak to sensitive issues like climate change and immigration.

Washington is the first leg of his six-day U.S. visit that will also take him to New York and Philadelphia later this week. While in New York, he plans to deliver a speech at the United Nations General Assembly on Friday. (Yonhap)