Negotiations on a strategic arms limitation treaty (SALT) fell short of success here today after the emergence of new issues which complicated the talks between the United States and the Soviet Union.

U.S. officials avoided explicitly saying so but they strongly suggested that the complications arose from the Soviet side.

It was clear that the two sides failed to settle the two major issues holding up agreement. These are encoding of Soviet missile test data and the definition of certain types of cruise missiles. In addition, some issues were raised that the U.S. side thought had previously been settled.

The unexpected turn of events dashed soaring hopes and produced grim faces and unusually long negotiating sessions totaling eight hours during the course of the day. But the talks ended with an official statement that most of the outstanding issues have been "essentially resolved," and that a U.S. Soviet summit meeting has been agreed on "in principle."

Soviet Foreign Minister Andrei Gromyko made it clear anew, however, that all major questions must be settled prior to the expected summit meeting of President Carter and Soviet leader Leonid Brezhnev. He added that some of the outstanding issues are "important."

In what amounted to a joint statement which was drafted by the two delegations and read by Vance, the foreign ministers said timing of the summit meeting will be "subject to careful consideration by both sides."

Lack of agreement in today's Geneva talks all but eliminates any chance that Carter will be able to play host to Brezhnev in mid-January for signing of a SALT treaty, as Carter had desired. Vance and Gromyko expressed hope that the remaining issues can be resolved through "regular diplomatic channels" without need for the two foreign ministers to meet again. Before the Geneva talks both men had expressed their intention to make this the last substantive negotiating session on SALT.

No date for the diplomatic contacts through admbassadors or the lower-level delegations of the two countries in Geneva was announced. In view of the Christmas and New Year's holdiays in the United States and the important New Year holdiays in the Soviet Union, little progress is expected until after the first of the year.

American negoitators insist that they are under no time pressure to reach a quick agreement although is is well known that the Carter administration is determined to present a new SALT pact to Congress early in its forthcoming session if at all possible.

A U.S. official who briefed reporters said, "We did what we could. We were not able to reach final agreement. This underscores the fact that we will not sign an agreement until we have what I believe to be a sound agreement and one which I and the administration can put before the Congress as . . . both sound and in the interest of the U.S. and its allies."

The official said "a couple of issues turned out to be much more complex and difficult than we thought they would be" in the Geneva talks.

American officials sounded surprised and somewhat mystified by the "less forthcoming" Soviet position which emerged this morning, but they said they did not know if it resulted from new Soviet instructions to Gromyko overnight.

Under other circumstances, a joint declaration that most issues had been resolved and a summit envisioned would be taken as a highly successful result. But this time, Vance and Gromyko had gone into their ninth round of talks on SALT with the hope and expectation of being able to resolve all basic issues still outstanding and then to make tangible arrangements for the summit.

After two days of successful talks, State Department spokesman Hodding Carter announced last night that the two sides are "close to the end of the road." Privately, officials were saying that approval from the Kremlin to several matters discussed with Grmyko was all that stood in the way of success.

Plans were made for Vance and Gromyko to hold a joint press conference after what was to be their final session this morning. Athis was to be followed by an extensive briefing to followed by an extensive briefing to acquaint American reporters with details of agreement which had been worked out.

In Washington, the White House contacted television networks about a possible request for air time for a presidential statement about noon today. The idea was for a Vance-Gromyko announcement on SALT this morning, followed by a joint annnouncement of the Carter-brezhnev summit from Moscow and Plains, ga.

All this was conditional on the results of the Geneva talks. "At not time was there a tentative agreement," said an American official here today, refuting press reports to the contrary.

Another offical said, "The thought the night before was that they would move this on through" to wind up the basic matters under discussion. He added that the two sides discovered this morning it could not be done.

The first outward sign of trouble defected by the waiting press corp was the failure of Vance and Gromyko to end their morning meeting on time after about 2* hours. It was more than four hours after their talks began an dafter Gromyko had planned to leave Geneva to return home that the two men emerged, grim-faced, from the Soviet mission.

Vance said tersely that "very little progress was made this morning at our discussion" and that an afternoon meeting was cheduled.

Gromyko agreed. He apologized for the long delay and said, "It is not we who are to blame but the logic of the talks." He added that "it is sometimes very hard in planning the start of negotiations to plan also the ending of them. And that is what happened today."

The reporters, many of whom expected the announcement of final agreement and a hint of summit talks to come, were monentarily stunned by the brief and somber exchange.

SALT experts of the State Department, Defense Department and National Security Council who ahd been scheduled to leave Geneva for home at midday were held back. Gromyko cancelled his plans to return to Moscow today and Vance delayed his plans for an afternoon departure for Brussels to meet Egyptian Prime Minister Mustapha Khalil and Israeli Foreign Minister Moshe Dayan.

Instead the two ministers, accompanied by three aides on each side, met again for more that 4 1/2 hours, their longest session during the current round of talks.

There were indications that the afternoon meeting was somewhat more successful than that in the morning but still far short of what had been expected. Asked if he were disappointed by the turn of events, the official U.S. briefer said that some progress had been made since the Geneva talks began on Thursday. He added, "You've got to be patient. You've got to persevere."