The commerce post had been vacant for nearly a year, since the businessman John E. Bryson resigned for medical reasons in June; his deputy, Rebecca M. Blank, has been acting secretary since then. Ms. Blank, an academic, is leaving to become chancellor of the University of Wisconsin, Madison.

Ms. Pritzker is chairwoman and chief executive of PSP Capital Partners and its affiliate, Pritzker Realty Group, and chairwoman of Artemis Real Estate Partners. During Mr. Obama’s first term, she served on his Council on Jobs and Competitiveness and on his Economic Recovery Advisory Board. Mr. Obama credited her on Thursday as “the driving force” behind his Skills for America’s Future initiative to connect businesses and community colleges to develop a work force with the skills employers need.

Mr. Froman, who is 50, has served in the White House as the deputy national security adviser for international economics since Mr. Obama first took office. Although the post was not a cabinet position, Mr. Froman had proximity to the president and a portfolio thicker than that of the cabinet-rank trade representative, encompassing not only trade but also international development and climate change issues.

Mr. Froman had planned to keep his White House post in the second term, and Mr. Obama initially intended to nominate Jeffrey D. Zients, a businessman who had been the acting director of the Office of Management and Budget, to be trade representative. But opposition to Mr. Zients from Senator Max Baucus of Montana, the Democratic chairman of the Senate Finance Committee, which would handle his nomination, scuttled it. Mr. Baucus objected to Mr. Zients’s oversight of a government-reorganization study that recommended changes that would have affected the committee’s jurisdiction, according to administration and Congressional aides.

Mr. Froman’s inclusion with Mr. Obama for the trip to Mexico and Costa Rica reflects his current leading role in international economic affairs. He has been the president’s “sherpa,” making preparations for past and coming global economic summit meetings. He also oversees economic relations with Europe, Japan and the developing BRIC bloc — Brazil, Russia, India and China — and development policies for Africa and the Middle East.

Administration officials said Mr. Froman would retain some of those responsibilities.

On Thursday, Mr. Obama gave Mr. Froman credit, along with the man he would succeed as trade representative, Ron Kirk, for finishing free trade pacts with South Korea, Colombia and Panama, all of which were begun in the Bush administration. The foremost issues for the new trade representative will be to negotiate trade liberalization deals with Europe and the Pacific Rim region.

“He has won the respect of our trading partners around the world,” Mr. Obama said of Mr. Froman. “He has also won a reputation as being an extraordinarily tough negotiator while doing it.”

Labor groups generally have had good if occasionally testy relations with Mr. Froman, but a liberal group, Public Citizen’s Global Trade Watch, assailed his “corporate agenda.” Business groups issued statements praising him and Ms. Pritzker.