It will be the first time in five years that the 13-time Grand Slam singles winner has broken up his early season schedule for the Davis Cup.
"I am excited to once again join my fellow Swiss teammates, who I have a great friendship with,'' Federer said on his official Web site. "I look forward to what I am sure will be a tough weekend.''
The World Group first-round series will be played March 6-8 in the U.S. at a venue to be chosen by the United States Tennis Association in the next six weeks.
Federer helped Switzerland rejoin the elite World Group when it beat Belgium last month.
He beat Kristof Vliegen in straight sets, then teamed up with Stanislas Wawrinka, his Olympic doubles gold medal-winning partner in Beijing, to win their doubles match.
Federer last played a Davis Cup first-round match in 2004, a victory over Romania in Bucharest.
"We are obviously very pleased that he decided he will be joining the team,'' Swiss Tennis spokeswoman Sandra Perez said. "That increases our chances.''
Swiss officials were hopeful Federer would face the U.S. because his tournament schedule takes him to California immediately after the Davis Cup for the March 9-22 Indian Wells tournament.
"Probably if we were playing the tie in Australia that would have been a little bit more difficult,'' Perez said.
Switzerland and the U.S. have a 1-1 record in Davis Cup meetings.
In 2001, Federer won three points - including singles victories over Todd Martin and Jan-Michael Gambill - when Switzerland beat the United States in the first round in his home city, Basel.
The U.S. beat the Swiss in the 1992 final at Fort Worth, Texas, with Andre Agassi and Jim Courier playing singles and John McEnroe and Pete Sampras in doubles.
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