NINETEEN European countries that stretch from the Arctic Ocean to the Mediterranean Sea clinched a deal Tuesday to create the world's biggest common market.The pact between the 12-member European Community and the seven-nation European Free Trade Association (EFTA) is likely to increase the continent's political clout and serve as a trial for ultimately enlarging the EC. "This is a tremendous achievement. It opens the way to the creation of the largest and most integrated common market in the world," EFTA President Pertti Salolainen, Finland's external trade minister, told a news conference. The agreement was reached after the two blocs found solutions on free trade in fisheries products, EFTA's financial contribution to the EC, and Alpine truck transit, all of which had threatened to block a deal. The officials said small technical problems remain to be settled, but none was seen as capable of blocking the merger. Under the common market deal, EFTA - consisting of Austria, Iceland, Lichtenstein, Norway, Finland, Sweden, and Switzerland - beginning in 1993 will implement hundreds of EC rules in their national legislation in areas such as the free movement of goods, capital, services, persons, and areas such as EC competition policy. The European Community consists of Belgium, France, Italy, Luxembourg, Netherlands, Germany, Britain, Denmark, Ireland, Greece, Spain, and Portugal.