President Obama arrived here early Saturday to start a three-country tour of Latin America, choosing to take this long-planned trip even as he manages the U.S. response to the crisis in Japan and possible military action in Libya.

White House officials emphasized that Obama could monitor both situations as he travels to another part of the world. Many of his key national security officials, including Thomas E. Donilon, the national security adviser, have joined him in Brazil.

Administration officials said it was important that Obama visit this region, which has not been one of the focal points of his foreign policy agenda. The trip is Obama’s first to South America, and his wife, Michelle, daughters, Sasha and Malia, and mother-in-law, Marian Robinson, stepped off the plane with him this morning after an eight-hour overnight flight.

“This trip — which some questioned, ‘How could the president go to Latin America on this long-planned trip, with everything happening from Japan to the Middle East and North Africa?’ — is being answered in the right way,” Secretary of State Hillary Rodham Clinton said Friday, a few hours before Obama departed. “Strategy depends on the ability to look deeper and further than the day-to-day. . . . The president is off to a trip that will take him to three important countries and send a message to all the others” in Latin America.

Obama is scheduled to spend Saturday trying to strengthen relations between the United States and Brazil, the most influential country in South America and its largest economy. The countries have had tense relations at times over the past two years, disagreeing over how to handle Iran’s nuclear program. But administration officials see an opportunity to repair the relationship with Brazil’s new president, Dilma Rousseff, who succeeded Luiz Inacio Lula da Silva.

Obama’s events Saturday include appearing at a meeting of chief executives of American and Brazilian companies and a speech on economic ties between the United States and South America that is likely to highlight Brazil as a market for U.S.-made goods.

“Growth in the Latin American market stands to benefit American workers and companies more than growth anywhere else in the world,” Clinton said.

In his weekly radio address, which was taped before he departed, Obama said, “One of the main reasons for my trip is to strengthen economic partnerships abroad so that we can create good jobs at home.”

Obama will leave Brasilia on Saturday for Rio De Janeiro, which is considered the cultural capital of Brazil. He will spend Sunday there before heading to Chile and then El Salvador.

The president is scheduled to return to Washington late Wednesday.