President Reagan yesterday called the $276 billion deficit-reduction target set by Congress last week a "good-faith beginning" toward reducing the federal deficit without raising taxes, but he warned that he will veto any bills that "contain excessive spending levels or might jeopardize our national security."

The president, in his weekly radio address from Camp David, Md., also pressed for passage of his tax legislation, and said his 1981 tax cut is the reason the economy has rebounded and inflation has dropped. The nation is facing "a new dawn of progress," he said.

But Rep. Ron Wyden (D-Ore.), in a Democratic response, said many of Reagan's budget cuts have been achieved simply by slashing health care for the elderly and deeply cutting federal medical research funds for such problems as Alzheimer's disease.

Wyden also challenged Reagan to carry out immediately a reported White House plan to take Social Security out of the unified federal budget, thereby removing any temptation for Congress to achieve budget cuts by cutting Social Security.

"Take Social Security off the political firing line," said Wyden. "Tell the American people that you are taking Social Security out of the hands of the budget-cutters. Tell them that this is more than just a bookkeeping change.

"But Mr. President, let's not stop there," said Wyden. He said the administration is limiting home health services for the aged and funds for Alzheimer's research, so "please call your health officials on Monday morning and tell them you want new policies so that home health care will thrive, not wither."

Wyden said he is happy that the president, after his colon operation, had advised people with early symptoms of disease to see their doctors for a checkup, but "more than 10 million Americans your age or older are trying to get by on $10,000 a year or less. They cannot afford your prescription."