Foreign ministers of the nine-member European Economic Community agreed here today that the EEC should "negotiate seriously" in an attempt to complete the Tokyo Round of trade talks as quickly as possible.

But this European response, couched in guarded terms and reflecting hard-line French opposition to yielding to what Paris sees as "the blackmail" over American extension of the countervailing duty waiver, appears to fall short of the firm commitment sought in Geneva last week by chief U.S. negotiator Robert Strauss.

Mr. Stauss went on record there with an urgent call for the trade talks to be concluded "by year end." Following his assurances to EEC negotiator Wilhelm Haferkamp that the administration would take "every available legal measure to avoid the disruption of normal trade flows" following the expiration of the countervailing-waiver authority on Jan. 3.

[Strauss said in Washington Tuesday that he is "pleased with the result" of the EEC members' talks, a result he said he "tried to obtain on my last two trips" to Europe. He said he hopped negotiations would be concluded by Christmas and that not to do so would "cause serious risk" to the world economy.]

[Administration officials added that they want legislation implementing any Tokyo Round agreement to be present to Congress by about March 15.]

But French Foreign Trade Minister Jean-Francois Deniau, commenting after today's lengthy discussions on what Strauss said last week, griped that "I cannot be satisfied with oral assurances which commit no one but the American administration." For Deniau, "nothing has changed" since countervailing duties first became a major EEC-U.S. controversy in early autumn "except that Congress has taken protectionist measures" and "has suppressed the waiver."

As a result, the French have refused to allow the other eight European governments either to agree to a Dec. 15 deadline for the talks set by the western economic summit held in Bonn in July or to increase the leeway available to European negotiators to facilitate their conclusion.

However, a more optimistic note is struck by spokesmen for other EEC governments, who all sought to play down the negative impact of the French position. They pointed out that European negotiators now are empowered to return to the Geneva headquarters of the trade talks to negotiate on all questions central to their successful outcome.

According to Court Otto Von Lambsdorff, West Germany's economics minister, all EEC countries except France share the view that the EEC should "try to come to results" in the talks "by Dec. 15." These results then should be sent to the Americans on the understanding that the European Community will be ready to sign the package only if the U.S. Congress extends the countervailing-duty waiver, he continued.

The Americans should be told that "you can take it or leave it, on condition that the waiver problem is solved," the German minister explained.

But even if EEC negotiators complete a package of this sort in Geneva by mid-December, they will have to run the gauntlet of what, on tonight's showing, looks likely to be an angry French government when they submit the package to foreign ministers for approval.