President Carter raised the possibility yesterday that he will veto the tax bill because the Senate refused to kill provisions he opposes. But he said he won't decide "until the bill gets to my desk."

The President made, the statement at a news conference yesterday morning after the Senate, in a direct rejection os his requests, voted 74 to 20 lote Thursday to retain two special tax credits for business which he wants dropped. To make the rebuff worse, the Senate immediately afterward voted to enlarge the credits from $3.3 billion to $4.1 billion over the fiscal years 1977-78.

"As you know, I am not in favor of continuing the business tax credit that the Senate voted yesterday," Carter said. He added, "My own position against the business tax credit has been very clearly expressed, and I will have to decide at the time the bill gets to my desk, if it passes, whether I can accept it or not."

Before the two Senate votes, many senators, including Finance Committee Chairman Russell B. Long (D-La.), had expressed the belief that the President wasn't all that strongly against the two business provisions and wouldn't veto the bill if they were kept.

Long went to the White House yesterday afternoon to discuss the bill with the President.

As he left, Long said, "A veto of the bill is always a possibility. We're not out of the woods yet", according to United Press International.

Later, his office issued a statement saying, "After our meeting this afternoon, I feel that President Carter has a better understanding of the tax bill in its present form in the Senate, and that the bill is well-balanced with more than 75 per cent of the benefits still going to individuals in the low-and-middle-income brackets."

This was a reference to non-controversial provisions permitting larger personal deductions and continuing a number of tax cuts for individuals which would otherwise expire at the end of this calendar year.

One of the two controversial provisions raises the investment tax credit, for businesses purchasing new equipment, from 10 per cent to 12 per cent for the years 1977 to 1980. This means a firm could subtract from its tax bill 12 per cent of the cost of new equipment and is intended to spur new investment.

The second provision permits a business, as an alternative to taking the added investment tax credit, to get a tax credit of up to $2,100 for each new person it puts on its payroll in 1977-78. This is intended to spur hiring of new workers by labor-intensive firms.

Last January, Carter asked Congress to approve a one-shot $50-per person tax rebate to individual tax-payers in order to pump $10.4 billion in purchaing power into the lagging economy. He also requested the investment tax credit increase and a payroll credit somewhat similar to the one in the Senate bill.

Last week Carter changed his mind, saying the economy had improved. He asked all three provisions be dropped. The Senate readily junked the $50 rebate, but on Thursday refused to drop the other two provisions, which are heavily favored by business organizations Long and many other Democrats argued against the President's position on the business credits.

Asked yesterday whether the President was threatening a veto over the two provisions, press secretary Jody Powell said, "He was deliberately not excluding a veto, he wants to keep his options open."

The Senate still hasn't finished work on the bill, and yesterday began debating a Republican amendment that would permanently cut income tax rates between 4 and 14 per cent on the first $20,000 of taxable income.

This proposal being pressed by Sens. John C. Danforth (R-Mo.) and Jacob K. Javits (R-N.Y.), would mean tax cuts for all, since those with taxable incomes over $20,000 would get the lower rates on the first $20,000. The cuts would start at a $36 reduction for a family of four in lower income brackets and rise in steps to $220 for those of taxable income of $20,000 or more. The proposal would reduce treasury revenues by $2.2 billion in fiscal 1977, $10.2 billion in fiscal 1978 and about $7.9 billion a year thereafter.

Danforth said the proposed cut would help avert an economic downturn being projected for 1978 and help reduce unemployment more successfully than the President's abandoned $50 rebate. But Sen. Edward M. Kennedy (D-Mass.) said passage of the permanent cut now, which Carter opposes, would be inflationary and make it impossible to enact broad permanent tax reform later because it would take away the tax relief that is usually needed to help a reform package get through. Carter had stated flatly that if the Republican amendment is passed next week, he will veto the bill.