U.S. President-elect Barack Obama is holding a national security meeting Monday in Chicago with his picks for the top diplomatic and security posts in his administration.

The meeting today includes Secretary of State designee Hillary Clinton; current Defense Secretary Robert Gates, who is to stay in that post;  Attorney General designee Eric Holder; and Mr. Obama's pick for secretary of homeland security, Arizona Governor Janet Napolitano.

Also attending the talks are the chairman of the Joint Chiefs of Staff, Admiral Mike Mullen; United Nations Ambassador designee Susan Rice; National Intelligence chief Mike McConnell; and National Security Advisor designee Jim Jones.

Separately, Mr. Obama is to hold a news conference later in the day (2200 UTC) to announce his energy and environmental teams and discuss the nation's future in those sectors.

Mr. Obama is expected to name Nobel physics laureate Steven Chu as energy secretary. Chu shared the 1997 Nobel Prize in physics for developing methods to cool and trap atoms with laser light.  He is the director of the U.S. Energy Department's Lawrence Berkeley National Laboratory in California.

Lisa Jackson, the chief of staff for the governor of the northeastern state of New Jersey, is expected to be named to head the U.S. Environmental Protection Agency.  She was previously New Jersey's environmental protection commissioner.

Mr. Obama is also expected to name former EPA chief Carol Browner to a newly-created post to coordinate policy on energy, the environment and climate change.

Separately, presidential electors - in their mostly ceremonial role - are gathering in their respective state capitals today to formally elect Mr. Obama as president.

Some information for this report was provided by AP.