He sent an e-mail to The Hartford Courant late Sunday, almost a week after the controversy erupted that stemmed from report published in the New York Times that he wrongly said more than once that he served in Vietnam.
"I have made mistakes and I am sorry. I truly regret offending anyone,'' Blumenthal said in the e-mail apology. "I will always champion the cause of Connecticut's and our nation's veterans."
Soon after media coverage of Blumenthal’s statements about his service, there were calls for him to apologize.
This is the first apology from Blumenthal, who said last week that he regretted that he misspoke and took responsibility.
Blumenthal served stateside in the Marine Reserve during Vietnam and received five deferments that, the New York Times reports, allowed him to avoid the war, travel abroad to study and to work in the White House.
He says he unintentionally said he served "in" Vietnam when he meant "during" Vietnam.
Blumenthal received the Democratic nomination for the Senate race Friday.