London — The British people are standing solemnly behind the government of Prime Minister Margaret Thatcher, even as officials here were hinting that Britain may have begun to invade parts of the Falkland Islands.
Signs of a hawkish public mood emerged in an opinion poll released May 9, echoing another issued a few days before, and in strongly pro-government results of local government elections in England and Scotland on May 6 following the loss of the destroyer Sheffield and three Harrier jump-jet aircraft.
Seventy percent of the May 9 poll (questioned on May 7 for commercial television) favored invasion of the Falklands if Argentina did not withdraw. Only 18 percent were opposed. Some 75 percent said that Britain could not accept any cease-fire without an accompanying Argentine withdrawal.
The poll was taken just after Argentina had rejected a cease-fire plan offered by Peru.
Findings like these mean that for the moment Mrs. Thatcher can continue her strategy of increasing military pressure on Argentina, both by public warnings here and by action in the South Atlantic, without fearing an immediate loss of public support.
The public mood could change, however, if the British fleet suffers more severe losses, if British deaths mount, or if Falkland Islanders themselves are killed in any attacks on Port Stanley.
On the United Nations front, talks continued May 9 between UN Secretary-General Javier Perez de Cuellar and representatives of Argentina and Britain. But Mrs. Thatcher was reported to believe that Argentina had no intention of withdrawing troops and that it was trying to drag out maneuvering at the United Nations in the hopes that severe winter weather would force the task force to turn back.
She was said to be determined not to allow negotiations to continue too long for that reason.
Current military strategy seems to be to keep the Port Stanley airfield out of action by repeated bombing runs, and to aim any troop landings at more remote and more lightly defended parts of West Falkland Island. (Other reports, however , speculate on a landing in East Falkland Island somewhere near Port Stanley.)
The latest opinion soundings here were taken as Britain extended its exclusion zone 12 miles from the mainland coastline and before the hurried diplomatic maneuvering May 8 and 9 at the United Nations in New York and among European Community foreign ministers in Brussels.
British Defense Secretary John Nott kept up the war of words here May 9 in a television interview. He said, ''We will not hold back from anything at all'' to protect the task force. He emphasized the fighting quality of professional, nonconscript British forces as well as what he saw as the weaknesses of the Argentine Air Force.
Argentina, he said, possessed only five French-built Super Etendard fighters of the kind that knocked out the Sheffield with an Exocet missile. Its Mirage fighters were 10 years old. With in-flight refueling (newly promised by the US, though Mr. Nott did not say so) Britain could fly as many more Harrier jets to the war zone as it needed.
While Argentina was tempted to ''play for time'' at the United Nations, he said, ''We can extend the blockade for far longer than their supplies could last (on the Falklands).''
The organization that conducted the commercial television poll, Opinion Research, said the findings were strikingly hawkish.
Only 38 percent were opposed to losing British lives, and 55 were in favor of military action even at the risk of British lives. The organization said the message to the government was: ''Don't weaken. Don't give in.''
The Conservative government received a strong boost from the local government elections because of what analysts call ''the Falklands factor.''
Normally the party in power loses considerable ground in midterm local elections, but the Conservatives held on to almost all their support, especially in southern England.
If a national election were held today, the Conservatives would lose only two seats in the House of Commons from the 332 they now hold, according to an analysis of the results by the Sunday Times newspaper.
The Labour Party retains support in Scotland and northern England. The Liberal Party did well. But the new Social Democratic Party did much less well than expected. One of the Social Democratic leaders, Roy Jenkins, said the Falklands crisis had swamped public attention during the campaign. As a new party, the Social Democrats relied heavily on continuing publicity while trying to put down local roots. During the Falklands crisis, this publicity had been impossible to obtain.
In a poll taken May 3 to 5 for the Economist magazine, 72 percent of 526 adults contacted favored landing troops on the Falklands, up from 65 percent in a poll of the same people a week before.
A majority still opposed bombing bases on the Argentine mainland, but the percentage in favor of such attacks had risen from 28 to 38 percent in three weeks.
Men were more hawkish than women. Men voted 2 to 1 in favor of risking loss of life, while most women were against it.
The Economist poll showed 53 percent willing to accept loss of life, up from 44 percent three weeks before.
On the diplomatic front, British officials appeared pessimistic May 9.
The diplomatic search for peace was like ''driving a car very fast through fog and able to see only 10 yards ahead,'' Sir Anthony Parsons, Britain's ambassador to the UN, told BBC Radio from New York. ''You don't know whether there is a brick wall ahead or sunshine. . . . You have to keep your eye on the road and keep driving.''
Mrs. Thatcher, however, appears determined that she will not negotiate or accept a cease-fire until Argentina has agreed to, and has begun to, withdraw its troops.
After that happens, she indicates, she might be prepared to settle for United Nations trusteeship of the islands as one way to safeguard the future of the islanders themselves.