Some further modest decline in the dollar still is acceptable to the Group of Seven major nations despite their communique late Tuesday night saying that the American currency had fallen far enough, U.S. sources said yesterday.

They noted that the key paragraph of the communique, dealing with the desirability of a stable dollar, says that "either excessive fluctuation of exchange rates, a further decline of the dollar, or a rise in the dollar to an extent that becomes destabilizing to the adjustment process could be counterproductive."

The operative word in the communique, which was arranged by telephone, is "could," it was explained yesterday. By saying that a dollar decline "could" be counterproductive, rather than "would" be counterproductive, the finance ministers were indicating that a dip in exchange rates below those prevailing when the communique was issued will be acceptable in some circumstances, sources said.

"You have to read the language. What if it {the communique} had said 'would be counterproductive'?" a source asked. "Those are very different words."

In any event, officials did not hide their intention to intervene in exchange markets, but intend to keep those markets guessing about the precise levels at which they will buy or sell currencies.

Beryl Sprinkel, chairman of the Council of Economic Advisers, told reporters yesterday that there had been no pledge in the G-7 communique to stabilize the dollar at a given level. He said the document had carefully avoided a pledge to support exchange rates "around current levels," a feature of the Louvre Accord and other G-7 agreements.

But a senior administration official Tuesday night said that the reference in the communique to avoiding "a further decline of the dollar" was based "on market conditions at the time of ... issue" of the communique: 11 p.m. EST. He added that that reference was "explicit in and of itself."

Although foreign exchange market dealers said they were disappointed that the "Telephone Accord" listed no new actions to combat trade imbalances, the dollar moved up slightly here and abroad in thin preholiday trading yesterday.

In Tokyo, the dollar closed at 126.55 yen, unchanged from Tuesday. Later in London, the dollar traded at 126.85 yen, up from 126.80 Tuesday. Other late dollar rates in Europe were 1.6390 West German marks, up from 1.6285; 1.3320 Swiss francs, up from 1.3255; 5.5425 French francs, up from 5.5160; 1.8440 Dutch guilders, up from 1.8370; 1,204.125 Italian lire, up from 1,199.75, 1.3065 Canadian dollars, up from 1.3049.

In New York, the dollar rose to 126.60 yen from 126.20 Tuesday, and to 1.6375 West German marks from 1.6260 the day before.

While U.S. Treasury officials refused any on-the-record interpretative remarks, finance ministers of the other G-7 countries were not hesitant to stress their view that the United States had finally responded to their pressure to call a halt to the dollar's decline.

West German Finance Minister Gerhard Stoltenberg, in commenting on the new G-7 accord, said in Bonn that a further fall in the dollar would be damaging to the global economy. And Japanese Finance Minister Kiichi Miyazawa pointed to the current dollar rate of about 126 yen as "acceptable," and said it was significant that the United States for the first time had joined in a statement opposing a further decline in the dollar.

British Chancellor of the Exchequer Nigel Lawson said the fact the United States had signed the communique meant that the Reagan administration does not want the dollar to decline further. He said he hoped officials here would back up the words with action, because -- in his view -- the dollar is now undervalued.

Lawson, who had been pressing the United States to accept higher interest rates to make the dollar more attractive, also had urged issuance of "Reagan bonds" -- securities denominated in foreign currencies -- to give foreign investors more security by transferring exchange rate risks to the United States. Although Treasury Assistant Secretary David C. Mulford had also favored that idea, it was vetoed for now by Treasury Secretary James A. Baker III.

The British official said he still believes that the Federal Reserve Board at some point will have to boost interest rates to curb domestic demand. But Sprinkel noted at a press briefing on the economy yesterday that the G-7 communique contained no commitment to higher interest rates, and, in fact, Sprinkel predicted a decline in U.S. interest rates.

"The {G-7} statement states explicitly that monetary policy should be directed at providing sufficient liquidity to encourage real growth while restraining inflationary pressures and promoting financial stability," Sprinkel said.