BRAZIL'S SARNEY MEETS STRIKES WITH SHOW OF FORCE With troops in place in Brazil's ports and oil installations, the government of Prersident Jose Sarney today sought to end a wave of labour unrest by a show of force. Yesterday the government sent thousands of troops supported in some instances by tanks to occupy nine oil refineries and six areas of oil production. The state-oil company Petrobras requested the intervention because of a threatened strike by 55,000 oil industry employees. The government had already dispatched more than 1,000 marines to occupy the country's main ports after a national seamen's strike was ruled illegal last Friday. The strike by 40,000 seamen, now in its 13th day, represents a stern challenge to the government. The stoppage has delayed exports at a time when Brazil desperately needs foreign exchange. It was a deterioration in the country's trade balance which precipitated Brazil's current debt crisis and the decision on February 20 to suspend interest payments on 68 billion dlrs of commercial debt. There was no sign today of an early end to the seamen's strike, which has badly hit the port of Santos -- the most important in South America -- and the country's other main ports. Small groups of marines armed with submachineguns stand on the quays near the strike-bound ships, but the military presence here is generally discreet. A total of 800 marines are inside the docks but most are out of sight. Yesterday marines and police occupied one ship, the Docemarte, seamen's leaders said. After explaining to the captain that the strikers faced up to one year in jail because the strike was illegal, the men returned to work. One of the strike leaders, Elmano Barbosa, said "it is a psychological war. They are using force and we are using peaceful methods." Port sources said only two Brazilian ships in Santos, the Docemarte and the Henrique Leal, were working. At the seamen's national strike headquarters in Rio de Janeiro, spokesmen say a total of about 190 ships are strike-bound in Brazil and in foreign ports. Contradicting earlier reports from strike headquarters in Rio de Janeiro, seamen in Santos said the strikers on board ships here were not running out of food. The current labour unrest is the worst faced by Sarney's civilian government since it came to power two years ago. Yesterday, in a separate protest, hundreds of thousands of farmers held rallies directed largely against high bank interest rates. The current rash of labour unrest in industry and agriculture stems from the failure of the government's now-collapsed Cruzado Plan price freeze.