President Reagan, asserting that Americans are "better off today than we were" because of his economic program, last night refused to accept responsibility for rising unemployment and recession and laid the blame instead on the Democrats who have dominated Congress since World War II. In his 13th nationally televised news conference, the president conceded that the unemployment rate may rise to a post-Depression high of 10 percent in next month's report, but he vowed not to change course in his economic policies.

Expressing empathy for the nearly 11 million people out of work, Reagan argued that nonetheless most Americans, even those on welfare, are benefiting from the progress the administration is making in bringing down interest rates and inflation, and thereby increasing purchasing power.

Last night's news conference, from the East Room of the White House, came in the midst of the fall congressional campaign, and several of the questions dealt with the impact that Reagan economic policies might have on the elections.

But the president brushed aside any responsibility for the nation's economic troubles, urged voters "to cut through all the demagoguery and rhetoric that they're going to hear," and declared that his administration had "pulled America back from the brink of disaster." He also promised that -- "unless there's a palace coup" -- he will not ask for tax increases next year.

Reagan denounced as "modern-day Rip Van Winkles" the opposition Democrats, who he claimed would like to forget the double-digit inflation, climbing unemployment and record interest rates he inherited. "No, we haven't solved 20 years of problems in our first 20 months in office," the president said in opening remarks. "But we have made a beginning where others failed to act."

Asked whether he would accept any responsibility for the nation's economic woes, Reagan quipped, "Yes, because for many years I was a Democrat."

But Reagan's contention that Democrats bear the responsibility for today's difficulties was immediately rejected by House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.). "The failure of Reaganomics is an American tragedy. President Reagan cannot pass the buck . . . . If the president really cares about unemployment, he would not veto so many jobs bills," O'Neill said.

With jobs the overriding issue in this fall's campaigns, Reagan acknowledged that when jobless figures for September are published Oct. 8 "it is possible that we might touch 10 percent."

Reagan sought to blunt the impact of what would be the highest level of national unemployment since the Great Depression with a claim that "there is a higher percentage employed today than has been true even in the past in times of full employment." He noted that even though 10.8 million people are out of work, 99 million are working.

"What has happened is a greater percentage of adult Americans have entered the work force--are in the work force--than ever before," Reagan said.

Reagan, attempting to lay the groundwork for what may be more bad economic news in the weeks ahead, suggested that one bad month wouldn't stand in the way of a recovery. "You've got to remember these figures are a little volatile," he said, motioning with his hands and adding, "you look at what is a chart line and there are dips in it . . . . And it may show a dip, but that will be a glitch."

But Reagan expressed confidence that the recession-wracked economy was "going around the corner or the curve" toward recovery. He insisted that his efforts to bring down inflation would cool interest rates still further and result in a permanent recovery and new jobs.

Asked if he would reconsider his economic game plan if unemployment continues to rise, the president responded with a firm rejection of the "artificial programs that make for dead-end and temporary jobs as we've had in the past.

"They don't last, they aren't permanent, and they also just delay the bringing back of the solid base to the economy," he said in rejecting a Democratic proposal to create 200,000 public-works jobs.

Making a plea instead for the job-training bill awaiting final congressional approval, Reagan said the legislation would provide 70 cents of each dollar spent for job training, compared to 20 cents in previous such programs. And he emphazied his belief that jobs are plentiful for those who want them and have the skills.

Reagan recalled that last spring he had pointed out the fat help-wanted sections of metropolitan newspapers. "There are still that many help-wanted ads, meaning there are that many open jobs looking for someone to fill them."

At the same time Reagan made clear his insistence on sticking with his economic program. He firmly refused to retreat from the third year of the tax cut due in July, 1983, and ruled out any tax increases next year.

Many economists and even some of Reagan's own advisers think he will have to accept yet another tax increase next year to reduce deficits and finance the military build-up. And Reagan in a later question referring to his promise not to raise taxes said that the earlier remark was only his "personal feeling" on taxes.

Reagan, in response to a question about whether the 1982 election would be a referendum on his presidency and economic program, sought to minimize any Republican losses. "You have to abide a little bit by tradition, that in that first off-year election, [of] any new administration, normally there is a great setback.

"Now, our opponents are saying they would hope to achieve 20 additional seats. Now, I think they're saying that because tradition has it that normally they get about 35 or 36 seats . And so they would like to be able to say, 'Oh, look how much better we did than we thought we were going to do.' "

Reagan was correct if off-year election House losses to the party holding the White House are calculated going back to 1922. However, from the Eisenhower years on, the party controlling the White House has lost on the average 12 seats in the first midterm elections.

Democrats have made a cornerstone of their fall campaign the charge that Reagan has unfairly favored the rich and hurt the poor. But the president insisted last night, "I think we're being more fair." He maintained that his cuts in social programs hadn't hurt Americans but that sometimes bureaucracts had erred in carrying out the programs.

But on balance, Reagan claimed, his efforts to bring down inflation have left even the poor with more money in their pockets. "People at the poverty level have about $600 more in purchasing power," he said, adding later, "Now, what is more fair?"