Friends of the family report that U.S. Senator Edward Kennedy is resting comfortably in the hospital while he awaits further tests to determine what caused him to suffer a seizure on Saturday.

Associates of the Democratic senator from Massachusetts said Sunday he was resting, eating and watching sports on television.

Kennedy's physicians said they are conducting a series of tests to try to determine the cause of his seizure.

On Saturday, the 76-year-old senator, who has served since 1962, was rushed to a hospital in Boston.

Kennedy has suffered health problems in the past. He had surgery last year to relieve a blocked artery in his neck.

Senator Kennedy is the youngest brother of the late President John F. Kennedy, who was assassinated almost 45 years ago.

The liberal lawmaker is an outspoken critic of President George Bush. Kennedy has also been one of the most prominent supporters of Senator Barack Obama's campaign for the Democratic Party's nomination in this year's presidential election.

Obama said Sunday he had spoken with Kennedy and that his fellow senator sounded like his old self. Obama said he was relieved to hear Kennedy's condition was improving.

Obama's Democratic rival, Senator Hillary Clinton, and presumptive Republican nominee Senator John McCain, both said their thoughts and prayers were with Kennedy.

Some information for this report was provided by AP and Bloomberg.