Britain and Argentina both know now who their friends are in the Falkland Islands affair.
Over the past week the members of the European Common Market lined up solidly behind the British.
The Soviet Union gave increasing aid and comfort to Argentina, which has become its single largest supplier of grain and meat (at the expense of US farmers).
The United States continued through this second week of the Falkland Islands affair to play the role of neutral broker between its official ally, Britain, and Argentina, to which it owes no official commitments and with which it has no long record of friendly cooperation.
The contrast between Washington's neutrality and the readiness of London's Common Market partners to join in a program of economic sanctions against the Argentines did not go unnoted in Britain. Opposition foreign policy spokesman Denis Healey joined leaders of the ruling Tory party in suggesting that Washington might have been more helpful to its usually closest friend and ally.
Washington was struggling during the week not only to head off shooting between Britain and Argentina, but also to dissuade Israel from invading Lebanon (which Israel was poised to do). Washington was also trying to hang on to reasonable relations with China while selling military spare parts to Taiwan over Peking's protest.
For the Reagan team, still less than a year and a half out of Sacramento, California, it must have seemed strenuous and confusing. It was grappling with three important world problems all at once with no background of experience in any of the three areas involved.
Its behavior shows that it has learned that it is important to retain good relations with mainland China. It seems still to be attaching less value to the NATO alliance than did its predecessors ever since World War II. It is a long way from mastering the problem of keeping on good terms in the Middle East with both the Arabs and Israel.
The affair of the Falkland Islands reached an interesting interim phase during the past week. The British fleet was heading south, being shadowed by Soviet reconnaissance ships, and reportedly also being studied by Soviet submarines, aircraft, and even satellites.
The Soviets in their public statements refrained from specifically approving the Argentine invasion of the Falkland Islands. Since the Soviets themselves occupy much territory claimed by others, Moscow is reluctant to sanction the idea of the use of force in such cases. But it accused the British of perpetuating ''colonialism.''
The US, meanwhile, in its role of ''broker'' was trying to find a formula that would satisfy the honor of both Britain and Argentina. This was made difficult during the week by the Argentines insisting on their flag continuing to fly over the islands as a symbol of ''sovereignty.'' The British cannot accept that without condoning transfer of territory by force.
While Haig grappled with the Falkland dispute, the top professional American diplomat at the State Department, Walter Stoessel, was shipped off to the Middle East. His task was threefold: (1) to head off a threatened Israeli invasion of Lebanon; (2) to keep the Israeli withdrawal from Sinai on track; (3) to try to get Camp David going again after the Israelis are out of Sinai. If Mr. Stoessel can do all three he will deserve a handsome bonus.
We do not yet know what the Chinese will actually do about the announced decision in Washington to sell $60 million worth of military spare parts to Taiwan. The Chinese have hinted that any sale of US weapons to Taiwan would put a freeze on US-China relations.
Moscow has been hoping for such a chill. It has been sending ''come-home-all-is-forgiven'' signals toward Peking. But so far Peking has failed to respond positively and has not downgraded relations with the US.