A top State Department official here vigorously defended American initiatives to foster competition in international aviation amid a chorus of complaints from the world's top airline executives that the United States is acting like an inter-national bully.

"I hear this charge constantly but I confess I find it difficult to understand," James R. Atwood, Deputy Assistant Secretary of State for Stransporation Affairs, told an international aviation conference sponsored by Lloyd's of London Press.

"I submit that the United States in attempting to implement its policies has proceeded moderately, responsible and non-coercively," he said. Although the policy approach has been controversial, U.S. actions in seeking to get liberal bilateral agreements with other countries have been exemplary compared to the way the rest of the world proceeds, he maintained.

The United States has never terminated one of its air services agreement as others have, choosing instead to abide by them even where they don't comport with present policy, he said. In contrast, he noted, many nations "are not above bending, if not totally fracturing" their agreements in order to implement their policy preferences.

Further, the United States has avoided using existing bilateral rights to create confrontation and gain leverage in bargaining, and it has kept strictly to aviation issues in its air negotiations, avoiding introduction of extraneous issues, pressures or inducements.

"The coercion argument is really reduced to the complaint that liberal agreements between the U.S. and one foreign country may affect air service between the U.S. and a neighbor of that first bilateral partner," he contended.

Atwood's defense followed some stirring denunciations of U.S. air policies by the top officials of Air France, Alitalia, British Airways and Qantas Airways.

Ross Stainton, chief executive of British Airways, who accused the United States of "arrant aerial imperialism," pointed - like others - to inconsistencies in U.S. policies. Nothing the Federal Maritime Commission seems to be pursuing a policy directly contrary to that of the Civil Aeronautics Board, Stainton asked, "How does the American government reconcile these views?"

"Are we seeing here a sharp edge of selfish, nationalistic mercantilism poking through all the glossy gift wrapping in which deregulation has been presented?

"Is the real reason the very sensible practical judgment that American airlines . . . stand a good chance of enlarging their markets at the expense of foreign airlines, while American shipping is in no shape to compete . . . ?"

If so, he suggested, European governments, who believe their airlines may not able to compete in a freely competitive environment, have "the best of reasons" to resist U.S. policies.

"We are not saying we are less efficient because we are stupid," Umberto Nordio, Alitalia's executive chairman, told reporters at a breakfast meeting. "But there are factors operating in Europe that we have to live with" like increased operating cost and air and airport congestion.

Nordional also brought up U.S. protection of its textile, shoes and appliance industries. "Why shouldn't European governments protect their airlines in the same way?" he asked.

Qantas Chairman Sir Lenox Hewitt also brought up U.S. import quotas on Australian beef to protect the domestic industry as "part of the great hypocristy."

"I don't claim we have perfectly consistent policies," U.S. State's Atwood replied. "But if you look at the aggregate of U.S. policies, we will stack up our record on free trade with all comers."

Atwood also sought to answer foreign critics who charge that the Civil Aeronautics Board is acting unilaterally in some of its initiatives, such as in reviewing U.S. approval of the rate setting activities of the International Air Transport Association, the trade organization of 103 world airlines.

He said State and the CAB had no "major" disagreements in policy direction and compared favorably the board's procedures to solicit views and modify proposed actions with the "more common closed-door approaches abroad."

All the critics admitted that the U.S. policies have had some beneficial effects in moving the world's airlines to become more efficient and in providing some lower fares for the traveling public. But they all urged the U.S. not to carry the policy so far that multilateral cooperation in preserving a world airline network was threatened. In particular, they urged U.S. acceptance of IATA as the operating frame-work for that cooperation.

In a related development, IATA asked the CAB to put off scrutiny of its rate-setting activities until the board had time to see how the organization would work under the new liberalized structure the board approved this month. CAPTION: Picture 1, Sir Lenox Hewitt of Qantas, left, listens to Umberto Nordio, chairman of Alitalia. AP; Picture 2, James R. Atwood defends U.S. airline initiatives at New York conference. AP