The Carter administration has decided to let Ronald Reagan deal with the $1.2 billion problem of foreign tax credits for the nation's oil industry, sources said yesterday.

The Treasury Department will release new regulations this week which will deal with some of the problems but will leave several of the major issues unresolved. The new regulations ease the restrictions on foreign tax credits in controversial regulations proposed in June 1979.

But the Treasury officials admit the new regulations still leave many problems for the oil companies, which lobbied hard against the original regulations. Donald C. Lubick, assistant secretary of the Treasury for tax policy, said yesterday that new legislation will be needed to solve these problems. "In my view you cannot do it under the present statute," Lubick said. The regulations will be effective, on a temporary basis, but also open for public comment for 60 days after their release. They will replace the earlier, temporary, regulations which have not yet started to bite.

The oil companies, and some other multinationals, complained that the original regulations would limit drastically the size of foreign tax credits the companies could claim. Their U.S. tax liabilities then would rise substantially.

Legislation on the issue was scheduled with the "windfall profits" tax but was shelved when the Carter administration agreed after urging from Sen. Robert Dole (R-Kan.) to re-examine the regulations and attempt to deal with the problem administratively.

Lubick said the new regulations will answer most of the complaints of manufacturing companies and banks who are affected by the foreign tax credit. But some oil companies still will get squeezed, he went on, although they will benefit from two modifications in the notice.

In recent years the huge foreign tax credits claimed by oil companies have been challenged by rulings from the Internal Revenue Service on the grounds that much of the "tax" paid overseas by the oil companies is not income tax. Only income tax presently is eligible for the foreign tax credit. This allows a U.S. company to offset, dollar for dollar, against its U.S. tax, however much it has paid in taxes overseas. Broadly, the regulations proposed in 1979 disallowed credits on any tax paid overseas if the tax was levied at a higher rate than the usual corporate tax rate in that country. They deemed that if that was the case, then the tax was not properly an income tax. The new proposals will allow oil companies to claim credits on part of the taxes paid, provided that the foriegn country says that it considers that part to be like an ordinary corporate income tax.

This, for example, would help some of those companies paying British taxes on their North Sea oil revenues. But other countries may not be willing to distinguish between income taxes and royalties.

Another change in the new regulations will be that companies may claim credits against tax levied before the realization of their income. At present a tax paid on oil before it has been sold and the company has made a profit is not considered an income tax. The oil companies would like to be able to claim the foreign tax credit on all of their overseas tax liabilities even if they are in the form of royalties rather than income tax. But a lot of companies will find that their overseas taxes are ruled not income taxes, Lubick said. In some cases the credits are allowed by treaty (as between the United Kingdom and the United States) but are not allowed to spill over and be offset against other earnings outside the country of extraction. He said the law would have to be changed if credit were to be allowed to the companies on taxes which were not income taxes. He said that "we would all have loved to solve it administratively" but that was not possible.

There also have been moves in Congress in the past to limit abuses of the tax credit by oil companies. Many of the companies pay a very high proportion of their overseas oil income in taxes, including royalties and excise duties. If the foreign tax credit exceeds a company's U.S. tax liability on that income, then it may offset the credit against other income tax liabilities, such as refinery earnings or shipping revenues.

Lubick said that in some cases oil companies had "sweetheart" arrangements with the countries where they were extracting the oil whereby the companies' pretax income and their taxes or royalties paid to the governments concerned would be inflated.This would leave the oil companies with the same amount of posttax income from those operations but with higher foreign tax credits.