U.S. President-elect Barack Obama has announced his nominees for agriculture and interior secretaries - two people he says are equipped to meet the country's energy and natural resource challenges.

During a press conference Wednesday in Chicago, Mr. Obama introduced former Governor Tom Vilsack of Iowa as his pick to head the Department of Agriculture.  Vilsack, a Democrat, is a strong advocate for developing alternative energy sources, known as biofuels, that can be made from farm products, such as corn.

Mr. Obama praised Vilsack for his work fostering what the president-elect called an "agricultural economy of the future."

The president-elect named Democratic Senator Ken Salazar of Colorado to head the Department of Interior, which manages the country's federal land.  Salazar has pushed to limit energy exploration in the western United States.   As interior secretary, he would oversee oil and gas drilling on government-managed land.

Mr. Obama announced Tuesday that he is nominating Arne Duncan to head the education department. 

The president-elect praised Duncan's reform work in Chicago schools and called him an independent thinker.

Mr. Obama also said improving the public education system is essential for the United States to remain a global economic leader in the 21st century.