Walter F. Mondale, setting the stage for the Monday unveiling of his deficit reduction package, today sought to shift the political onus of the tax increase it will contain onto President Reagan.

"As I said in my acceptance speech, Mr. Reagan will raise taxes and so will I. What I should have said as well is that this is not my tax. This is Reagan's tax, to get rid of his deficit," Mondale said following a meeting here with Georgia Democratic leaders.

"On Monday I will present my proposal to the American people," the Democratic presidential nominee added later at a citizens forum in Chattanooga, Tenn., "and then I will demand that Mr. Reagan presents his plan. Let's see it, Mr. Reagan."

Mondale called Reagan's deficits "nothing less than slow economic suicide" and accused the president of trying to duck reality by not spelling out a plan to deal with them.

"Their message is, 'No problem, we'll tell you what we're going to do about the deficits -- after the election,' " Mondale said.

"Americans have never dealt with the future by ducking reality," he said earlier in the day at Agnes Scott College in Decatur. "You can't walk away from these issues. They get worse if you try."

In his acceptance speech at the Democratic National Convention in San Francisco, Mondale pledged to cut the federal deficit by two-thirds by fiscal year 1989, and he took the political gamble of declaring he would raise taxes to do it.

Since then, his strategists believe he has scored with the public for candor and aggressiveness while keeping Reagan on the defensive.

On the other hand, they acknowledge that the strategy also has invited a Republican counterattack branding Mondale as a big taxer. At the meeting here this morning, several of the Georgia Democrats told the nominee that he must find a way to throw off that charge if he is to have a chance with Southern voters.

"The point Mondale needs to make is that these taxes aren't for bigger government, they're for paying off Reagan's deficit," said Hamilton Jordan, former chief of staff to President Jimmy Carter.

Others who attended the closed-door breakfast session included Gov. Joe Frank Harris, Lt. Gov. Zell Miller, state party Chairman Bert Lance and Sen. Sam Nunn (D-Ga.).

Mondale was forced to cancel a campaign appearance in Georgia last month when none of those men was willing to change plans to appear in public with him -- a reflection in part of the bruised feelings that linger over Mondale's handling of his short-lived appointment of Lance to be his campaign general chairman.

Mondale called today's meeting "excellent" despite reports that the governor, who has been notably lukewarm in his public comments about Mondale, attended only at Lance's urging. Harris did not join the others in meeting with reporters following the breakfast.

When Mondale reveals the details of his deficit reduction plan Monday in Philadelphia, his first order of business will be to set forth his projection of what that deficit will be in five years.

The Congressional Budget Office has projected the fiscal 1989 deficit at $263 billion, and the Reagan administration has projected it at $162 billion, an estimate that Mondale has ridiculed as "blue smoke and mirrors."Mondale is expected to use a figure much closer to the CBO estimate, and that would mean having to show budget cuts and tax increases in the $150 billion to $170 billion range.

In January, when Mondale presented a $100 billion budget deficit reduction package, he arrived at it in the following way:

*Sixty billion dollars in new taxes raised from a 10 percent surcharge on those who earn more than $100,000 a year, cutbacks in tax indexing for the wealthy, creation of a 15 percent minimum tax for corporations and loophole closing.

*Seventy billion dollars in budget cuts, with the bulk coming from the Defense Department, agricultural programs, health care costs and deficit interest expenses.

*Thirty billion dollars in new programs, mostly for education, research and efforts to assure trade competitiveness. An aide said the same "principles" were being used in drafting the new plan.