The United States and its allies kept up pressure Thursday on Lebanese Shiite leader Nabih Berri to unconditionally release the American hostages held in Beirut. The chances for a quick diplomatic settlement to the two-week-old crisis seemed reduced when France declined an offer by Mr. Berri to transfer all 39 hostages to the French Embassy in west Beirut.
``France is ready to welcome free people but not hostages,'' the French Foreign Ministry said. ``We cannot act as substitute jailers.''
Nevertheless, diplomatic activity continues, keeping alive hope that the situation might be resolved peacefully. Secretary of State George Shultz said Thursday that US officials were working intensely for the unconditional release of all Americans held in Lebanon -- including seven who have been kidnapped in the past 15 months.
Syria is now believed to be pressuring Berri to find an end to the hostage dilemma, which has heightened tensions between the US and Syria and between Israel and Syria.
``In Syria, there is fear that the Israelis would strike not Lebanon, but Syria militarily if the hostage crisis will drag on and if any of the hostages were hurt,'' said one Western diplomat. ``The Syrians know the Israelis would not hesitate if they thought it was Syria preventing a solution.''
One reason Syria is pushing for an end to the crisis could be that it does not want radical Shiite fundamentalists to gain the upper hand in Lebanon. Syria fears such a development could reduce its influence in Lebanon, some analysts say.
In Bern, the Swiss government announced it would accept the hostages into its embassy, but only if no conditions were attached to their transfer. The Swiss said they would accept the hostages if they were assured that they would be allowed to transfer the hostages to their territory or elsewhere.
At time of writing there was no immediate response from Berri, who is negotiating for the Shiites who hijacked TWA Flight 847 on June 14. It would be a major concession, however, for the Shiite leader to accept such a transfer with no public promise from the US that 735 Lebanese being held in Israel would be freed.
Alternatively, Berri said Wednesday, the hostages could be flown to Damascus and put under Syrian control.
Berri said he would turn over the hostages if whoever took them promised they would be released only when the hijackers main demand was met. The hijackers have asked that 735 Lebanese -- mostly Shiites -- being held in Israel be freed and returned to Lebanon.
Western diplomats in Beirut indicated Wednesday that they thought Berri's plan offered a way out for the stalemate that has existed in the crisis for several days.
Putting the hostages under the control of a Western embassy, these diplomats pointed out, would eliminate the most immediate concern for their safety and allow Israel to release batches of the Lebanese it holds while maintaining it was not giving in to ``terrorist'' demands.
The Reagan administration has continued to insist that it will not negotiate with the hijackers and that Berri should immediately free the hostages. The US also has said it will not ask Israel to release the Lebanese, although Israel has said it would consider such a request.
Even as Reagan spoke of resorting to such actions as blockading Beirut port and closing the airport, the Israeli Cabinet met secretly Wednesday night to discuss Berri's offer. No official statement was issued after the meeting, but Israeli newspapers reported that the government was willing to release the Lebanese.
The prisoners were carried across the Israeli border last April in a move condemned both by the International Red Cross and the US. Israeli officials earlier this week took pains to stress that Israel has always planned to release the Shiites, who have never been charged with crimes.
But both Israel and the US remain determined not to be seen bowing to the hijackers' demands. The two allies have worked hard at cobbling over differences that emerged between them in the early days of the hijacking, and now seem inclined to step up pressure on the Shiites.
``It has been made very clear to Berri by a number of diplomats that the Americans will not give in,'' said one Western observer. Berri, who is both leader of the mainstream Shiite militia, Amal, and Lebanon's minister of justice, is showing signs of stress as the crisis wears on.
There are reports that he had secretly traveled to Damascus earlier this week and met with Syrian President Hafez Assad. Syria, with 30,000 troops in Lebanon, is that nation's chief powerbroker.
``The Syrians are almost in 100 percent control of the situation now,'' said one Western diplomat in Beirut.
In the early days of the hijacking, the diplomat said, it was unclear how much control Berri, had over the situation. A more radical Shiite faction actually carried out the hijacking. Even after Berri stepped in as negotiator, he confirmed that some of the hostages were not under his control.
But Wednesday, Berri said he could deliver all the hostages, indicating he has consolidated his control for the moment.
``The way the affair is handled now clearly says that the hijackers are out of the game,'' the diplomat said.
In turn, Berri is relying on Syria, on whom he has become increasingly dependent in recent months, according to the diplomat. Berri's Amal militia suffered a military setback last month when it failed to eliminate Palestinian guerrillas loyal to PLO chief Yasser Arafat from the refugee camps of south Beirut.
Amal had boasted that it would take over control of the camps in a few days. Instead, after a month of fighting and many casualties, the Palestinians continued to resist. A settlement reached between the warring factions in Damascus -- with only anti-Arafat groups representing the Palestinians -- has imposed an end to the fighting that allows the Palestinian guerrillas to keep their light arms and stay in the camps.
Berri's dilemma is that, while he would like to see a resolution to the crisis, he cannot afford to be seen to have crumbled under pressure from the US and Israel.
Berri, an essentially secular man in charge of a movement that is becoming increasingly, militantly Islamicized, ``is in the middle of this mess, trying to take command,'' said the Western diplomat.