A new joint fund-raising initiative between Mitt Romney and the Republican National Committee will aim to raise $800 million by November, part of what Mr. Romney’s campaign estimates will be a total of $1 billion spent to defeat President Obama and elect Mr. Romney, a former Massachusetts governor.

Campaign Cash News and analysis on campaign fund-raising.

The goals were laid out in a memorandum circulated by Mr. Romney’s top fund-raisers in recent days and on a conference call with donors late last week. The memo indicates that Mr. Romney’s top aides hope to collect a total of at least $500 million for the campaign and for the joint fund, known as Romney Victory, through a program for high-dollar donations.

They are also hoping to bring in $300 million in smaller donations, an area where Mr. Romney has so far lagged well behind other Republicans candidates and Mr. Obama but where the Republican committee has performed relatively well. The campaign also estimates that “super PACs” and other outside groups will spend another $200 million in the race, according to the memo.

People closely involved in Mr. Romney’s fund-raising efforts said last week that they expected the campaign’s share to total about $600 million. Much depends on Mr. Romney’s ability to win the allegiance of hundreds of top Republican “bundlers” — those who raise money on behalf of a campaign — who did not commit to a candidate during the nominating contests. And it is common for campaigns to low-ball the targets they circulate among top fund-raisers, so as to beat expectations down the road.

Republicans have suggested that Mr. Obama, who raised about $750 million during his first run for president, will ultimately raise $1 billion for his re-election effort. The president’s campaign has vigorously disputed that estimate as a myth intended to motivate conservative donors and to convince Mr. Obama’s grass-roots donors that he does not need their money.

The $800 million goal includes about $86 million that the memo states Mr. Romney has raised during the Republican primary campaign. Mr. Romney reported raising $75.6 million through the end of February, suggesting that his campaign has taken in roughly $10 million more since the beginning of March. The Republican committee raised $13.7 million in March, the committee’s best month of the cycle so far.

But Mr. Obama and the Democratic National Committee raised $53 million during the same month, part of a well-oiled joint fund-raising operation that started last spring and has already staged over one hundred major fund-raisers. That figure, which includes money the Democratic committee raises on its own, was announced in a video posted early Monday morning on the campaign’s Web site.

Donors said in the video that 567,000 people donated to the campaign in March, and the average contribution was $50.78.

The video did not disclose how much money the campaign gathered in small checks versus large ones, or break down how much of the $53 million went into the campaign, which can take a maximum of $5,000 from each donor, and the Democratic committee, which can raise $30,800 from each donor each year.

More complete figures — along with detailed records of how much the campaigns and parties spent in March — are due to be filed with the Federal Election Commission by Friday.