With terrorists claiming they will not relent on their threat to blow up a hijacked Lufthansa jet with 92 persons aboard and kill a kidnaped West German government today sent what it called a "very important message" to the terroists only hours before the utlimatum was to expire.

The hijackers apparently working with the West German Red Army Faction, kidnapers of industrialist Hanns Martin Schleyer, are demanding that notorious terrorists in West German jails and two Palestinians in Turkish jails be freed and out of the two countries by early Sunday morning.

At the Persian Gulf airport in Dubai, where the Lufthansa jet is being held. West German and United Arab Emirate officials continued to try to negotiate with the hijackers. Earlier, the terrorists rejected appeals to let the women and at least half a dozen children off the plane.

Initial ultimatums delivered by both terrorist groups indicated that the plane would be blown up and Schleyer killed by 3 a.m. Greenwich Mean Time, or 4 a.m. EDT, unless their jailed comrades were free and safe by that time.

Some confusion was introduced, however, when the Arabic-speaking hijack leader in Dubai, who calls himself Mahmoud, sent a message to the West German ambassador there saying "the deadline is 1200 GMT Sunday. There will be no extension of this deadline. The plane will be blown up."

West German officials here could not explain the time difference, which means that the Bonn government may have until 3 a.m. EDT at least to deal with the situation.

West German Chancellor Helmut Schmidt, looking grim, met repeatedly into the night with his Cabinet, political leaders and security chiefs as the Bonn government agonized over one of the toughest decisions it has ever had to make.

West Germany has been victimized in the past six months by a resurgence of leftist terrorisim that has stunned the country. The chief federal prosecutor was machine-gunned to death in April. A leading banker was murdered in July, and Schleyer was kidnaped 41 days ago.

The attacks have been carried out by a small but efficient band of terrorists who have frustrated police efforts thus far to track them down. The urban guerrillas are all followers of the notorious Baader Meinhof gang that spread urban terror here in the late 1960s and early 1970s.

Included among the 11 jailed terrorists the hijackers want freed are three surviving members of that original gang - Andreas Baader, Jan-Carl Raspe and Gudrun Ensslin.

Thus, if Bonn yields to the demands - which also include a $15 million ransom - it almost guarantees that West Germany will face an ever more severe terrorist problem.

In the final 24 hours before the first deadline, pressures were clearly rising in Germany. In Dubai, the Lufthansa pilot of the hijacked jet sent a message to Schmidt saying "you are our last and only hope." The plane apparently is held by four terrorists, two of whom speak Arabic.

The defense minister of the United Arab Emirates, who is helping the West Germans negotiate with the hijackers, sent a cake aboard the stranded jet to a stewardess for her 28th birthday.

In Germany, the family of Schleyer in an eleventh-hour bid to save his life filed suit in federal constitutional court to force the government to yield to the demands because of the state's obligation under the constitution to save the lives of individual citizens.

Bonn announced that a special jet carrying a squad of anti-terrorist police that had been standing by for two days in Turkey was heading back to West Germany

This could be a sign that the Schmidt government has decided to give in to the hijackers or it could be a plov. Though Bonn has given virtually no details of the Schleyer case it made public Friday the fact that this special plane had trailed the hijacked Lufthansa 737.

The government here gave no details of what was in the "important" message sent to the terrorists via Swiss lawyer Denis Payot, who has been serving as an intermediary to the Schleyer kidnapers.

The prisoners are scattered in four different prisons and a prison hospital in West Germany.

The terrorists have said their comrades should be sent to South Yeman, Somalia or Vietnam. A Somali diplomat, according to reports here has indicated that his country would accept the prisoners if it could help save lives. Both South Yemen and Somalia are near Dubai.

The Turkish government reportedly is waiting for the Bonn government to make its decision before making its own on whether to release its prisoners.

The Boeing 737 was hijacked Thursday shortly after takeoff from the Spanish island resort of Mallorca en route to Frankfurt. Unexplained thus far is how, during a period of heightened tension because of the Schleyer kidnaping, four terrorists with guns and hand grenades got past airport security.