"At times when I have sought to honor veterans, I have not been as clear or precise as I should have been about my service in the Marine Corps Reserves," Blumenthal said in a statement e-mailed to the Hartford (Conn.) Courant late Sunday by his spokeswoman, Maura Downes. "I have firmly and clearly expressed regret and taken responsibility for my words.
"I have made mistakes and I am sorry. I truly regret offending anyone. I will always champion the cause of Connecticut's and our nation's veterans."
Blumenthal has come under criticism since The New York Times reported last week he had stated incorrectly several times through the years that he served in the Vietnam War. Blumenthal was in the Marine Corps Reserves in the United States during the war and received five draft deferments.
Last Tuesday, he expressed regret for having "misspoken" about his service but stopped short of saying he was sorry at that time.
Blumenthal, 64, won the Democratic nomination Friday as he seeks to win the seat held by Sen. Christopher Dodd, who is retiring. Linda McMahon, a professional wrestling industry executive, former U.S. Rep. Rob Simmons and money manager Peter Schiff are running on the Republican side.
Notable deaths of 2014 [PHOTOS]