PORT-AU-PRINCE, Haiti — First lady Michelle Obama made a surprise visit Tuesday to the ruins of the Haitian capital, a high-profile reminder that hundreds of thousands remain in desperate straits three months after a devastating earthquake.

The first lady and Jill Biden, wife of Vice President Joe Biden, took a helicopter tour of Port-au-Prince before landing at the destroyed national palace to meet President Rene Preval. They later talked with students whose lives have been upended by the disaster and walked along a vast, squalid encampment of families living under bedsheets and tents.

“It’s powerful,” Obama told reporters. “The devastation is definitely powerful.”

A number of past and present world leaders have visited since the earthquake, including former Presidents Bill Clinton and George W. Bush. But few have the star power here of the American first lady, whose husband is widely popular in Haiti.

“It was important for Jill and I to come now because we’re at the point where the relief efforts are under way, but the attention of the world starts to wane a bit,” she said. “As we enter the rainy season and the hurricane season . . . the issues are just going to become more compounded.”

The United States has provided nearly $1 billion in humanitarian aid to Haiti and pledged more than $1 billion in additional aid. While underscoring the U.S. commitment, the visit by Obama and Biden also served to thank American officials who have worked in the country for the past three months, the administration said.