The Finance Committee also has tax-related questions for former Senate Democratic leader Tom Daschle of South Dakota, nominated as secretary of Health and Human Services. No date has been set yet for action on Daschle’s nomination.

The Judiciary Committee is scheduled to vote Wednesday on the nomination of Eric H. Holder Jr. to be attorney general.

The confirmation of Obama’s choices for EPA administrator, former New Jersey environmental chief Lisa P. Jackson, and White House Council on Environmental Quality chairwoman, Nancy H. Sutley, were delayed because a senator has put a hold on their nominations, a Democratic aide said. The identity of the senator holding up the nominations and the reason for blocking them could not be immediately determined.

Fast Start Sought

Obama’s nominees — those facing delay and those confirmed Tuesday — joined Obama, Vice President Joseph R. Biden Jr. , congressional leaders and other dignitaries in the Capitol’s Statuary Hall for the traditional post-inaugural luncheon.

Stressing the challenges his new administration faces, Obama has repeatedly vowed to waste no time filling key posts and implementing new policy directions.

Reid said Tuesday, “These challenges require a president with a full arsenal of tools and experts. President Obama has nominated a Cabinet of exceptionally bright and capable people. . . . It is up to us, Democrats and Republicans in the Senate, to confirm these worthy nominees quickly so that they, along with our new president, can hit the ground running.”

Chu, 60, a physicist who won the Nobel Prize in 1997, has run the Energy Department’s Lawrence Berkeley National Laboratory since 2004. Chu has called the threat of climate change one of the most urgent challenges of our time, and as head of the laboratory, he directed research efforts in renewable and alternative energy technology.

His appointment to head the department signals a major shift for an agency that has chiefly focused on managing the nation’s nuclear arsenal and nuclear science programs. It’s also likely to elevate what has long been viewed in Washington as a second-tier agency.

Duncan, Obama’s choice for secretary of Education, is a personal friend of the president’s who has been CEO of the Chicago Public Schools system since 2001. He championed charter schools, stressed teacher quality and shut down or restructured underperforming schools.

During his Jan. 13 confirmation hearing, Duncan said that as Education secretary, he wants to raise standards at the K-12 level, work to increase teacher quality, reward innovation and increase access to higher education. Part of the latter task will include ensuring that students continue to have access to the federally backed student loan program.

Duncan also will have to take a specific position on the reauthorization of President Bush’s No Child Left Behind law (PL 107-110), something Obama has thus far avoided.

Napolitano, a border-state Democratic governor from a Republican-leaning state, was among the first to call for using the National Guard to police illegal immigration at the border. But unlike the Bush administration and Congress, she has not supported large-scale border fencing projects.

OMB director Orszag, who will play a key role in helping enact a massive economic stimulus plan, was director of the CBO for nearly two years before Obama named him as his budget chief after the November elections. Before his stint at CBO, Orszag, a former top economic adviser to President Clinton, was deputy director of economic studies at the Brookings Institution.

Salazar, who was elected to the Senate in 2004, resigned effective upon his confirmation as Interior secretary, a job that gives him broad sway over the management of public lands across the West and elsewhere. Colorado Gov. Bill Ritter Jr. , a Democrat, has selected Michael Bennet, the superintendent of Denver Public Schools, to fill Salazar’s seat for the final two years of the former senator’s term.

Shinseki publicly disagreed with the Bush administration about the size of the forces needed to stabilize Iraq after the 2003 invasion, telling a Senate committee several hundred thousand more troops would be needed than administration officials wanted.

The disagreement was a factor in Shinseki’s tense relationship with then-Defense Secretary Donald H. Rumsfeld, which culminated in Shinseki’s retirement June 11, 2003, after four years as Army chief of staff.

Shinseki has echoed Obama’s promises to overhaul the VA to allow veterans to transition from military to civilian life without having to worry about benefits being available when they need them.

Building on his work as Iowa governor, Vilsack is expected to bring new attention to health and climate change at USDA, which has traditionally focused heavily on crop production.

At his confirmation hearing, he said his priorities would be fighting childhood hunger, safeguarding the farm economy, promoting renewable energies and resolving civil rights complaints against the department.

Vilsack will be working with Congress on implementation of the 2008 farm bill and reauthorization of a law governing school lunches.

Vilsack, an attorney with the business law firm Dorsey & Whitney, cut short his bid for the presidential nomination in 2007 and endorsed Clinton. He stumped aggressively for Obama after Clinton withdrew.

David Clarke, Coral Davenport, Lydia Gensheimer, Kathleen Hunter, Catharine Richert, Matthew M. Johnson and Aliya Sternstein contributed to this story.