WASHINGTON, Oct. 27, 1983 (UPI) -- President Reagan vowed Thursday night to maintain the U.S. military presence in Lebanon, saying to withdraw now would ''dishonor'' the 225 Marines killed in the Beirut bombing.
Reagan, in a nationally televised address on the crises in Lebanon and Grenada, said the United States ''has strong circumstantial evidence'' that Sunday's attack on the Marines ''was directed by terrorists who used the same method to destroy our embassy in Beirut."
''Those who directed this atrocity must be dealt justice. They will be,'' Reagan said in his televised address from the Oval Office.
''We will do everything we can to ensure that our men are safe as possible,'' he said. ''We are doing our best to make our forces less vulnerable to those who want to snipe at them or send in future suicide missions.''
He mourned the deaths of the American servicemen but said this ''tragic price to pay'' must not weaken U.S. resolve.
''We cannot and will not dishonor them now and the sacrifices they have made by failing to remain as faithful to the cause of freedom and the pursuit of peace as they have been,'' Reagan said.
The Pentagon earlier Thursday raised the death toll in Sunday's bombing to 225.
The Marines died as they slept in a barracks at the Beirut airport, the base for the U.S. contingent of the multinational peacekeeping force in Lebanon for more than a year. A terrorist drove a truck into the U.S. compound, crashed into the barracks and detonated 2,000 pounds of explosives.
''The obvious purpose behind the sniping and now this attack was to weaken American will and force the withdrawal of U.S. and French forces from Lebanon,'' Reagan said. ''The clear intent of the terrorists was to eliminate our support of the Lebanese government and to destroy the ability of the Lebanese government and to destroy the ability of the Lebanese people to determine their own destiny.''
''Brave men have been taken from us. Many others have been grievously wounded. Are we to tell them their sacrifice was wasted? They gave their lives in defense or our national security every bit as much as any man who ever died fighting a war. We must not strip every ounce of meaning and purpose from their sacrifice.''
Reagan delivered a strong defense of the U.S. presence in Lebanon in an attempt to answer the question, ''Why are we there?''
The president called the Middle East a ''powder keg'' and cited Soviet advisers in neighboring Syria and the strategic importance of the region to vital U.S. interests.
''If that key area should fall into the hands of a power or powers hostile to the free world, there would be a direct threat to the United States and to our allies,'' Reagan said.
''Let me ask those who say we should get out of Lebanon: If we were to leave Lebanon now, what message would that send to those who foment instability and terrorism?
''If America were to walk away from Lebanon, what chance would there be for a negotiated settlement producing a unified democratic Lebanon?
''If we turned our backs on Lebanon now, what would be the future of Israel?''
Reagan cited a string of ''tragedies'' for the 1,600 Marines during their stay in Lebanon, including those killed by sniper fire before Sunday's bombing.
''I called bereaved parents and-or widows or the victims to express, on behalf of all of us, our sorrow and sympathy,'' he said.
''Sometimes there were questions and now many of you are asking, 'Why should our young men be dying in Lebanon. Why is Lebanon important to us?'"
''So why are we there?'' Reagan asked. ''The answer is straightforward: to bring peace to Lebanon and stability to the vital Middle East. To that end, the multinational force was created to stabilize the situation in Lebanon until a government could be established and a Lebanese army mobilized to restore Lebanese sovereignty over its own soil as the foreign forces withdrew.''
''With patience and firmness we can help bring peace to that strife-torn region -- and make our own lives more secure,'' the president said. ''Our role is to help the Lebanese put their country together, not to do it for them.''
Reagan did not announce a replacement for Robert McFarlane as his special Middle East envoy. But he promised a replacement for McFarlane, his new national security adviser, ''soon.''
Former Defense Secretaries Donald Rumsfeld and Melvin Laird have been mentioned as possible appointees for the job.
Reagan did not say who he was referring to as being responsible for the April 18 bombing of the U.S. Embassy in Beirut. The embassy was devastated by a car bomb, killing 63 people including 17 Americans.
Defense Secretary Caspar Weinberger has cited ''circumstantial evidence'' that followers of Iranian leader Ayatollah Khomeini were responsible for both the embassy and Marine barracks attacks.