NEW YORK (Reuters) - Many United States Democrats welcomed Mrs Hillary Clinton's move to quell the controversy over her use of a personal e-mail address to conduct government business, but some said her remarks still left questions. "I think she handled it well, but I do have to question: I have two e-mail accounts and I only have one device," said Democratic donor Gabor Garai, a lawyer in Boston who raised about US$50,000 (S$69,312) for President Barack Obama in 2012.

Mrs Clinton's decision to address reporters reflected a calculation among her advisers that the issue was ballooning into crisis-like proportions. The story has dominated cable news for days. "By waiting so long to finally show her face and address it, I think it just allowed this thing to spiral out of control," said a former Clinton adviser, who spoke on condition of anonymity. He noted that the crisis revealed Mrs Clinton did not have a capable campaign-in-waiting with a sharp media strategy to counter such criticism. Speeding up the formal announcement of her run would allow such infrastructure to be put in place.

Republicans, who have questioned her ethics and transparency, were not convinced of her efforts so far. Representative Trey Gowdy, a Republican who chairs a congressional committee looking into the Benghazi, Libya, attacks of 2012, said she left "more questions than answers" and pledged to call her up to Capitol Hill for further testimony. Critics raised concerns that the arrangement allowed her to hide important facts about her tenure and put her correspondence at a security risk.

Mr Ari Fleischer, a former spokesman for Republican President George W. Bush, scoffed at Mrs Clinton's explanation for the account. "Personal convenience? Hah. She did it because she only trusts a few top aides and wanted total control," he wrote in a tweet.

It is not unusual for officials in Washington to have two mobile devices.

The White House has said it encourages administration officials to use government email accounts, though rules on whether personal e-mail accounts can be used on government-issued devices appeared to vary among agencies.

Asked about former secretary of defence Chuck Hagel's e-mail practices, a Pentagon spokesman said he carried two Blackberrys while he was in office, one for personal and one for government business but may, on occasion, have sent e-mail to or from the wrong account.

Mrs Clinton said she had provided all her e-mails that were work-related to the State Department and did not keep personal e-mails on subjects such as yoga routines, her mother's funeral arrangements or her daughter's wedding plans.

But she also said the private server contained communications from her and her husband, an apparent contradiction to her statement that e-mails had been deleted.

Mrs Clinton defended the practice on Tuesday as a matter of "convenience", but her comments failed to calm critics, who accused her of secrecy.

The prospect of numerous e-mail deletions and her argument of "convenience" gave more fodder to Republican critics who accused her of continuing secretive practices that they say characterised the Clinton family and President Bill Clinton's eight years in office.

Holding her first news conference since leaving her administration post two years ago, Mrs Clinton conceded she wished she had used a government e-mail address as secretary of state but said she violated no rules and did not send classified material through the private account.

"I opted for convenience to use my personal email account, which was allowed by the State Department, because I thought it would be easier to carry just one device for my work and for my personal emails instead of two," a self-assured Mrs Clinton told more than 200 reporters crowded into a United Nations corridor. "Looking back, it would've been better if I'd simply used a second e-mail account and carried a second phone."

Most of her official e-mails were sent to government addresses, which were automatically preserved, Mrs Clinton said. Her family's server had not been hacked, and she rejected calls that it be studied by an independent arbiter.

The State Department said on Tuesday it would post Mrs Clinton's e-mails on a website after a review that was likely to take several months. Mrs Clinton tried to head off criticism last week by urging the department to quickly review and release her e-mails.