President Obama and Democrats report raising more than $114 million for 2012 campaign in August, marking their best fundraising month of the election cycle and outpacing rival Mitt Romney for the first time in three months.

The Obama campaign announced the figure on Twitter ahead of formally filing financial reports with the Federal Election Commission by Sept. 20.

Read more about August fundraising totals.

The August total, which includes funds collected by the president's campaign committee, Democratic National Committee and joint fundraising accounts, is a significant increase over the $75 million raised by the groups in July. Romney reported raising $111 million in August.

Obama campaign manager Jim Messina credited a surge in grassroots donations for the strong showing.

"The key to fighting back against the special interests writing limitless checks to support Mitt Romney is growing our donor base, and we did substantially in the month of August," Messina said in a statement.

"Fueled by contributions from more than 1.1 million Americans donating an average of $58 - more than 317,000 who had never contributed to the campaign before - we raised a total of more than $114 million," he said. "That is a critical downpayment on the organization we are building across the country - the largest grassroots campaign in history."

The Obama campaign said last week that more than 3.1 million Americans have donated to the president's re-election effort, surpassing the total of four years ago.

The average donation last month was $58, the campaign said. Ninety-eight percent of donations were $250 or less.

"No celebrating," tweeted @BarackObama in response to the numbers, "because they're going to have an even bigger September. But now we know we can match them, doing this our way."