WASHINGTON - Democratic presidential candidate Hillary Clinton said on Friday she was sorry that her use of a personal email account while secretary of state had caused confusion, and blamed herself for "not thinking a lot" about the matter when she took the job.In her most contrite comments yet about an issue that has plagued her White House bid, Clinton said she had made a mistake by not using a government email account. But she maintained she had done nothing wrong and did not apologize explicitly for using a private email account for her work as America's top diplomat."At the end of the day I am sorry that this has been confusing to people and has raised a lot of questions but there are answers to all these questions," the former first lady told MSNBC in an interview.Clinton, front-runner to be the Democratic Party nominee in the November 2016 election, has faced steady criticism from political opponents since it emerged in March that she used her own email account on an unsecured private server in her New York home for official business. Republicans say she flouted rules on record-keeping and transparency."I certainly wish that I had made a different choice and I know why the American people have questions about it," said Clinton, who was secretary of state from 2009 to 2013. "I take responsibility. I should have had two accounts, one for personal and one for work-related."Doubts over Clinton's trustworthiness have damaged her numbers in opinion polls, allowing liberal Vermont Senator Bernie Sanders to narrow the gap with her before the first contests early next year to pick the Democratic Party nominee for the election.