Beirut — The bearded young Iranian charge d'affaires sat relaxed in a velvet chair in his spacious office. ''Unfortunately, every time America has a loss in the region, it blames Iran.
''It used to blame everything on the Soviet Union. But since the Islamic revolution, it says everything bad is from Iran,'' Majid Kamal explained.
''We strongly reject these charges of involvement'' in the bombing of the United States Marine and French contingents of the multinational peacekeeping force in Beirut. The charges were first announced by Defense Secretary Caspar Weinburger.
''Some of this is a joke,'' the Iranian diplomat said, getting angry about reports that his embassy was the center for planning the massive blasts that have so far claimed more than 260 American and French lives.
''They are all lying. We don't know anything about this,'' Mr. Kamal said firmly. ''This is just part of a satanic plan'' to allow an excuse to retaliate against Iran because the US ''is afraid after our statements about shutting the Strait of Hormuz (oil route) and afraid of a victory by the Islamic Army against Iraq in the new offensive (in the Gulf war).''
Less than five miles down the road, US Vice-President George Bush, dressed in a flak jacket and helmet, was touring the wreckage of the former Marine battalion headquarters. Deeply moved by the grueling round-the-clock rescue operation, he said:
''I hadn't expected this much destruction. You heard it. You read it. But until you see it, see the size of those reinforcing steel bars, and then I guess the horror, just the cowardly horror of what happened.''
Mr. Bush also grew angry, declaring resolve that ''US foreign policy is not going to be dictated or changed by terror'' - a statement that explained his brief surprise trip to the Lebanese capital Wednesday.
As the vice-president moved off, under extraordinary security, for talks with President Amin Gemayel, another Lebanese leader's temper was on edge. Visibly livid by statements from an unnamed US official in Saudi Arabia that the Shiite Muslim group ''Amal'' was linked to the two attacks, Amal chief Nabih Berri countered:
''If they can't prove it, I have to ask the Americans especially to leave all Lebanon,'' he said at a press conference. ''It is something like racist against Shiites all over the world.
''I warned many times that something might happen. They can't blame us.''
The separate and disparate displays of anger underline that the Sunday bombings have left far more damage than at the Marine compound, for tension has escalated dramatically throughout the Middle East since US officials began making quick-on-the-draw accusations about who was responsible.
The threat to retaliate has triggered further fears. Beirut newspapers reported Wednesday that key politicians had received information in anticipation of ''major security events'' in the capital's predominantly Shiite southern suburbs. And many residents prepared themselves for a new round of fighting, convinced that the Marines would soon sweep through their areas.
In Syria, another country tipped by US officials as a link in the chain of responsibility, the state-controlled newspaper Al Baath warned, ''Any aggression on Syria would constitute a threat to world peace, for Syria would not be alone in the battlefield.'' It was a reminder of Syria's security pact with the Soviet Union.
And the Iranian charge d'affaires predicted President Reagan would order retaliation ''everywhere that he can'' against Iran, including the embassy in Beirut. ''We are just waiting to be martyrs,'' Kamal said.
The anxiety and mutual suspicions have badly marred the atmosphere surrounding the Lebanese reconciliation talks that are scheduled to begin in Switzerland next week, in which all parties believed to be tied to the blasts have a major role or influence.
It is also likely to make the Marine presence even more controversial - and uncomfortable. But the French government has said nothing specific about the bombing of its facility while investigations continue, thus so far avoiding diplomatic altercations.
Indeed, there are growing doubts about the US ability to carry through on either accurately naming those involved, or retaliating. Col. Hisham Jaber, Lebanese Army liaison with the Marines, described the bombings as ''the perfect crimes'' because ''they left no evidence.''
And a young Marine lieutenant noted, ''My boys would like nothing better than to know. Nobody wants to leave with their tail hanging between their legs. But somehow I doubt we'll ever really know.'' It has not gone unnoticed that those responsible for the US Embassy bombing last April, which killed more than 60 Americans and Lebanese, have still not been named.
There is also little optimism that the path for the Marines - and the other three contingents of the multinational force - can be smoothed out, for none of the alternatives are practical, say key peacekeeping participants.
''I think they should either pull us out or let us loose,'' said a corporal who was badly injured in the attack. Many other survivors share his sentiments.