President Reagan yesterday backed partially away from his effort to force new budget cuts through Congress before the end of the year and spoke out strongly against raising taxes in 1983 or 1984 to help reduce federal budget deficits.

Reagan opened his fifth White House news conference with a strong defense of his economic program. "This government must stiffen its spine and not throw in the towel on our fight to get federal spending under control," he said.

In answer to a question, however, the president revealed that there was at least a little terrycloth on the floor; he indicated he was scaling back the $13 billion in spending cuts and $3 billion in increased taxes he proposed only 6 1/2 weeks ago, on Sept. 24.

Reagan repeated his demand that non-defense appropriations be cut 12 percent below the levels he first proposed last spring, and his threat to veto "budget-busting" bills. But, yielding in part to opposition that sprang up in Congress within his own party from members who either were unenthusiastic or wanted to amend his proposals, Reagan backed down in the non-appropriations parts of the budget.

He said his promised cuts in the basic benefit or so-called entitlement programs that make direct payments to individuals and any discussion of tax increases will be deferred until January.

Reagan said this did not mean dropping such plans "in any way." He said: "Those programs were never intended to go into effect until late in 1982 anyway. So even in January, we will be--if that is the route we take, they will be in time for when they originally were scheduled." White House deputy press secretary Larry Speakes explained later that although these plans will be delayed until January they will still be part of the 1982 budget, not part of the 1983 budget, which will be proposed at the same time.

Reagan said the delay was necessary because there is no time to get Congress to act earlier.

"The problem has been, with the Christmas holidays coming, after all our discussions with our leaders in Congress, that we just can't produce or get anything done by Congress in this interim period and so it's the best advice that since they don't have to be set back by delaying their presentation until January, that's when we're going to do it," he said.

The only action on federal spending he wants from Congress before the end of the year, Reagan said, is passage of the required appropriations bills with his 12 percent cuts included, or if necessary, of a continuing resolution that would cover departments without appropriations bills and would also provide for the 12 percent cuts.

"Fiscal 1982 is already five weeks old, but I have not received a single, regular appropriations bill. Most of the bills pending are over-budget," Reagan said, and he reiterated his threat to veto "budget-busting bills."

"I stand ready to veto any bill that abuses the limited resources of the taxpayers," Reagan declared. In an apparent attack on Democrats who still control the House, Reagan added: "It's ironic that those who would have us assume blame for this economic mess are the ones who created it. They just can't accept that their discredited policies of tax and tax, spend and spend, are at the root of our current problems."

Both the delay and Reagan's statement opposing tax increases represented defeats for budget director David A. Stockman. Stockman, joined by influential Republican senators, had urged Reagan to impose more tax increases than he proposed in September to avoid what they fear could be huge budget deficits. The tax cut and defense spending increases Congress voted at Reagan's request last summer will drive up the deficit despite the $35 billion in domestic spending cuts already approved and the additional cuts Reagan will propose in January.

"You could always balance a budget if you put it on the backs of the people with tax increases," he said. "I don't favor that at all, because every time you do that you find that it's like getting addicted to a drug, because of the very fact that those tax increases then reduce the prosperity and the productivity of the nation further and you find that you need more of the same and more of the same."

"The reduction of government spending is the answer," he said.

Reagan gave up last week on his commitment to balance the budget by 1984 and declined yesterday to set a new target date, but he said a balanced budget remains his goal.

He echoed predictions by his economic advisers that the current recession is going to cause some hard times, but that the economy will revive in the spring or early summer. He cited the recent 3 1/2-point decline in interest rates as an encouraging sign.

The president also looked forward to the impact of the personal income tax cuts that will take effect in July, but in claiming that his economic program is only 40 days old did not mention that his business tax cuts are already in place retroactive to last Jan. 1.

In response to a question, the president said that his budget cuts have not jeopardized the well-being of people "with real need."