Fear and uncertainty have invaded the presidential palace of Ferdinand Marcos, replacing the confidence and bravado Marcos and his few remaining loyal aides had been voicing just 24 hours ago.

In the neighborhoods around the Malacanang Palace, apprehension spread quickly as elite troops of the Presidential Security Command moved into defensive battle positions on the palace grounds. Residents fearful of being caught in the cross fire of a final stand by a still defiant but less confident Marcos began to flee to safer areas of the city.

"All the transient people from the neighborhood, the students, or people who have places to go to in the provinces, they're leaving," said Sandra Reico, an insurance company employe.

Within hours, that fear turned to reality when a helicopter dropped a grenade on the palace compound and tense troops later opened fire on civilians demonstrating in support of the rebels.

The isolated incidents appeared to reflect Marcos' increasingly defensive posture. Within a day, he had moved from threats of using military force to crush the rebels to appeals to loyal troops to gather around Malacanang to protect him and his family, whom he described as "cowering in terror" inside the palace.

"Forgive me the informal dress," Marcos said in a broadcast carried early Tuesday by a television channel owned by a close associate. "We are not going to abandon the office of the presidency. We are not going abroad. I have no intention of resigning. We will defend the republic to the last breath of our life, the last drop of our blood."

On Monday, by contrast, Marcos was relaxed when he called reporters to a televised press conference to counter reports by the Roman Catholic Church-run Radio Veritas that he and his family had fled the country. Soldiers in freshly pressed fatigues escorted journalists into an elegant chamber of the palace.

Marcos' wife Imelda looked calm as she spoke to reporters near an alcove holding statues of Catholic saints lit by dozens of small candles.

In that press conference, Marcos solemnly pronounced the nation in a state of emergency, but ridiculed suggestions from reporters that he might be losing control of the country.

In an exchange during the conference, Marcos refused a request by his military chief, Gen. Fabian Ver, for permission to launch an air strike against the headquarters of the rebel army forces demanding Marcos' resignation.

During the exchange, Ver, standing at attention before Marcos' desk, leaned forward slightly as he pleaded with Marcos, "We cannot withdraw all the time, Mr. President."

As before, Marcos said he had avoided attacking the rebels to prevent civilian casualties. But he insisted that he would fight the dissidents.

As reporters left the press conference, gardeners continued to lay sod for the Tuesday inauguration of Marcos. Two tanks flanked the newly built platform from which Marcos planned to deliver his inaugural address.

But within half an hour, military officials sent palace employes home. Shortly afterward, a tank on the palace grounds fired its cannon and machine gun at a helicopter that reportedly had dropped a grenade on the compound. Inside the palace press section, some people dropped behind desks at the firing, while others leaped to the windows. "Well, the foreign correspondents wanted a civil war," one palace employe said bitterly. "Now it looks like they'll get it."

A few minutes later, an officer of the Presidential Security Command announced to a handful of foreign correspondents: "We can no longer guarantee your safety. You will have to leave now."

As the journalists left, soldiers carried armloads of weapons and ammunition to rooftops and sandbag emplacements. One young marine, smoking nervously, whispered, "We've never fought [within] the Army. I don't know if they [anti-Marcos rebels] will shoot at us."

Air Force, Army and Marine units guarded a perimeter about 500 to 600 yards from the palace. On Mendiola Street, a 22-year-old soldier named Rene faced the taunts of anti-Marcos crowds across a barbed-wire barricade. He wore a white armband.

"It's a sign of peace," he said. "We don't want to fight our brothers, and we will not fire at them if they don't fire at us."

Residents of Manila's San Miguel district, which surrounds the palace, watched the soldiers and worried that their poor and middle-class neighborhoods might become a battleground.

Bystanders debated conflicting reports from the rebel and loyalist radio stations that Marcos either had fled the country or remained in the palace.

Arturo Buan, a lawyer in his thirties, said: "People are just waiting for the big event. We just don't know which big event it will be."

Young women from the Holy Spirit College, across the street from the palace, walked past children playing catch in the streets and carried their suitcases and bags out through the loyalist defensive perimeter.

"One thing is sure," said insurance company employe Reico. "The people don't want Marcos anymore. But his position, his family, everything he's worked for is at stake, and I don't know if he knows how to give up."

Almost in the shadow of the palace, along a canal filled with raw sewage, residents gathered outside a dilapidated tenement and talked quietly with a visitor.

"Very afraid, very panic," said a woman, carrying her son.

They explained that they could not leave because they had no place to go to wait out a standoff between rebels and Marcos' loyalists.

"Maybe the soldiers will come tell us before the fighting starts," a young man said. Pointing to a narrow path between the edge of the canal and a row of shanties, he said, "We could go out that way."

Should Marcos flee the country? they were asked. At first, no one answered. The young men exchanged glances. Gloria, a housewife, said quietly, "It's better if he just goes, and leaves the country in peace. Otherwise, there will be a civil war."

The young men nodded, and Diony Mesina, 24, an unemployed auditor, spoke. "My soul is happy because we will have freedom now," he said. But, he continued, searching for words, "my body is nervous because I don't know what will happen to us today and tomorrow."