A FIERCE QUARREL has broken out within the Carter administration, as you may have noticed over environmental regulation of certain U.S. exports. Suppose the Export-Import Bank, a federal agency, finances the sale of nuclear equipment to another country. Should the Ex-Im Bank have to write an environmental impact statement - one that would be subject to attack in U.S. courts? A lot of countries would regard that as infringement of their sovereignty.

But suppose, again, that American foreign aid buys pesticides for an agricultural development project in an undeveloped country. Does the United States have an obligation to tell the recipient what it knows about the environmental effects of those pesticides? Most Americans would say that it does and, in fact, the Agency for International Development already requires environmental statements for its projects.

The President's Council on Environmental Quality is leading the campaign to apply American environmental law to some exports - those that the federal government subsidizes or licenses. The opposition comes mainly from the State Department and the Ex-Im Bank. One thing that they fear is repeated collisions with other governments over regulatory authority. When the United States started to run preliminary environmental studies on the proposed gas line from Alaska down through the Yukon to the Midwest, Canada tartly told the American experts to stay on their own side of the border. Canada thinks, with some reason, that its own standards are at least as high as this country's.

Another fear is litigation tying up decisions on exports, and embroiling foreign buyers in the American courts. The Council on Environmental Quality reflects a tradition of public-interest lawyering that considers the threat of litigation essential to strict enforcement of standards. But law suits are a poor way to make foreign policy.

The rules on environmental protection abroad will have to vary with circumstances. There's not much dispute that American operations in the deep oceans and Antarctica - what lawyers call the global commons - need to be held to the same standards as in the United States. No other country's jurisdiction is involved. Foreign aid does involve other jurisdictions, but the United States bears a broad responsibility for the consequences for its advice to undeveloped countries.

It's the commercial sales - and above all, the sales of nuclear reactors and fuel - that raise the hard issues. Some buyers will welcome an American environmental impact statement, since it requires the seller to disclose what he knows about the effects of the product or the project. But what if the buyer's government considers the American requirements to be an intrusion? One solution is to require an environmental statement only if the foreign government agrees. Otherwise the collision of sovereignties becomes unmanageable.

As for nuclear exports, safety standards are far too important to be left to the ambiguous and unsettled provisions of American environmental law. When American reactors go to countries with no great depth of technical experience, they need to be accompanied by the most explicit safeguards. That is the Nuclear Regulatory Commission's job. The present attempt to take the environmental law abroad is grounded in the environmental organizations' suspicions that the NRC tends to tilt in favor of the nuclear industry. The remedy to those suspicions does not lie in the slow and uncertain processes of the federal courts. It lies in the White House. That's what the country has a President for.