London — The seven leaders of the major Western industrial countries have dispatched a gentle invitation to the Soviet Union to end its ''hibernation.'' A Soviet response is not expected until after the presidential elections in the United States. Nonetheless, all seven, and not just the US, made it clear at the London economic summit that the door is open.
''We are determined to pursue the search for extended political dialogue and long-term cooperation with the Soviet Union and her allies,'' stated a special summit declaration on East-West relations and arms control.
''We wish to see early and positive results in the various arms control negotiations and the speedy resumption of those now suspended.''
This London summit, concluded Saturday, is notable in that its political declarations are at least as important as its economic actions.
Compared to their statements at Williamsburg, Va., one year ago, the summiteers used considerably softer language in dealing with the Soviets.
Last year they confirmed their plans to go ahead with the deployment of Euromissiles to counter those installed by the Soviets. This year, at the urging of Canada's prime minister, Pierre Trudeau, (who has been dubbed the ''summit peacenik'' by officials here), the special statement included a section on the ''common interests'' of East and West. These, the statement noted, include preserving peace, enhancing confidence and security, reducing the risks of surprise attack or war by accident, improving crisis management techniques, and preventing the spread of nuclear weapons.
The soft approach also suited President Reagan, concerned about progress in arms negotiations and hoping to improve his image among voters at home (and elsewhere) of being overly hawkish. Indeed, Mr. Reagan was the chief target of tens of thousands of antinuclear demonstrators that clogged central London Saturday. Police said they had arrested 214 people, mostly for obstruction, but no violent incidents were reported.
Another political move was a separate declaration on international terrorism. The declaration calls for blacklisting nations abusing their diplomatic immunity.
Following the practice of each leader getting some political bonus from the summit, the seven further issued a ''declaration on democratic values.''
A third statement on the Persian Gulf war expressed ''deep concern at the mounting toll in human suffering, physical damage, and bitterness'' that the four-year-old Iran-Iraq conflict has brought. It supported any efforts, including those of the United Nations Secretary-General, to seek ''a peaceful and honorable settlement.''
There was no call for an arms blockade or any other concrete action. But the seven said rather vaguely: ''We shall do whatever we can to encourage stability in that region.'' The statement did call for a stop to attacks on shipping in the Gulf. And they referred to their ''will and capacity to cope with any forseeable problems'' in regard to world oil supplies.
On the economic side, the leaders presented a 12-page communique that included a 10-point program of action to ''sustain the economic recovery, to create new jobs, and to spread our prosperity much more widely across the world, '' as Mrs. Thatcher put it in a concluding press conference.
The statement shows considerably more concern with the problems of the developing countries than those of previous summits. For example:
* The leaders said they were ''standing ready where appropriate'' to negotiate multi-year reschedulings of developing country debts owed to governments and government agencies.
Until now, commercial banks have been willing to reschedule only those debts coming due in the next 12 months or so in negotiations with debtor nations. However, because of the improvement in the financial condition of Mexico, the bankers have been talking of rescheduling Mexico's debts over the next three or four years.
The Federal Reserve indicated its backing for such a move at a convention of major international bankers in Philadelphia early last week.
Now the summit leaders also have given their backing to the commercial bankers, along with a pledge to consider the same step in regard to government loans to the developing nations.
This action, however, will not be considered adequate by those economists calling for caps on interest rates or other measures to reduce the debt burden for the poorer nations.
Indeed, France has been calling for a new issue of $15 billion in Special Drawing Rights - a type of international money - which presumably would help the developing countries service some of their debts. However, the biggest expense involved in such an issue would fall on the US, West Germany, and Japan. A new issue of Special Drawing Rights is to be considered by the so-called Interim Committee of the International Monetary Fund in September.
* Summit members spoke of the need to take ''due account of political and social difficulties'' faced by the debtor countries when tackling their international payments problems. But the leaders, though referring to these economic and financial policy changes as ''painful and courageous,'' also termed them ''necessary.''
* The summiteers spoke of increasing the flows of resources, including government aid, to the developing countries. But no new money was visible.
The industrial nations urged the developing countries to open their economies to investment from the industrial countries. Such equity investment does not have to be repaid in the short term, like bank loans, but can await profitability and the ability to pay dividends.
In the conciliatory tone of the statement, the same clause mentioned how the industrial countries must make their markets more open for the exports of the developing countries.
As expected, the industrial nation leaders could only agree to consider going ahead with a new round of trade negotiations ''at an early date.'' Japan wanted these by 1986, but France refused to be so specific.
The West German government, troubled politically at home by the environmentalist Greens, sought and got a section on environmental concerns.
On interest rates, the United States blocked any specific mention of its high deficits. The communique merely called for reduction of deficits ''where necessary.''
US Treasury Secretary Donald Regan noted at a press conference that he has for four summits challenged his counterparts in other nations to offer proof of a close relationship between the level of deficits and of interest rates with no response.
But officials of such nations as Britain, West Germany, France, and Canada continued to make much fuss about high US interest rates, worrying that they might dampen their economic recoveries.