Most West European governments have welcomed President Reagan's Nov. 13 decision to lift sanctions on firms involved in the Siberian natural gas pipeline.
But they are leaving the impression that agreements made by them in return for the United States ending the ban are imprecise and do not form part of a formally agreed package agreement.
Some European officials are going so far as to say that they have helped President Reagan get off a hook he himselft baited in the wake of the military clampdown in Poland last December.
In Brussels, the European Commission hailed the decision to lift the sanctions, as an ''important step toward the stabilization of relations between the European Community and Washington.''
But France formally declined to be a party to the agreement, which sets guidelines for trade with the Soviet bloc in strategic materials. Officials in London say the understanding now coming into effect will restrict export of high technology, curb subsidized credit, and freeze new natural gas contracts with the East.