Minutes before a powerful bomb ripped through their northwest Washington home in the muggy, predawn hours yesterday, Yugoslavia's charge d'affaires, Vladimir Sindjelic, and his wife, Leposava, were trying to calm their whining German shepherd watchdog. Astra.

"Astra, budi mirna!" the diplomat's wife whispered to the attack dog in her native tongue. "astra, be quiet," she repeated.

At that moment, a bomb planted in the window flower box outside their downstairs sitting room exploded, sending bricks and glass flying, twisting their copper gutter into a pretzel shape, tearing limbs from pine trees in the yard and shattering windows in four nearby homes.

No one was injured, but the 4 a.m. explosion rocked the exclusive "Gold Coast" neighborhood, brought puzzled and badly shaken residents into the streets in bathrobes and drew a crowd of predawn rubbernecks to the corner of Quincy and Argyle streets NW. Several said they had heard the explosion miles away.

"I scared me," said Terrence Grant, 34, counselor at the Gordon Adult Education Center and a Vietnam veteran who was awakened in his apartment at 3626 16th St. NW, blocks away. "It sounded like a mortar attack. I thought for a second I was back in Vietnam."

No one claimed responsibility for the bombing of the $200,000 home at 1907 Quincy St. NW. But the FBI was investigating "the possibility that the bomb was planted by one of the anticommunist Yugoslavian terrorist splinter groups" that have launched a number of violent attacks against Yugoslavian government personnel and installations aboard in recent years, an FBI spokesman said.

One State Department official viewed the bombing as political -- an attempt to protest President Carter's scheduled trip later this month to Yugoslavia. The trip is designed to shore up American ties with the post-Tito regime in Belgrade.

About the time of President Tito's death, May 4, American officials had anticipated such violence, and warned Sindjelic and other Yugoslav diplomatic officials throughout the United States to be "very cautions." U.S. authorities had provided with additional "protection from time to time response to specific threats," Sindjelic said in a 6 a.m. interview in a neighbor's living room. But there was no guard stationed outside the home yesterday morning.

The dog had tried to warn him, too, Sindjelic said as he recalled the moments leading up to the explosion.

Plagued by insomnia, his wife had just turned off the late-late show in her upstairs bedroom. Sindjelic was fast asleep in the other. Downstairs, house guest Slobodan Pesic, 23, their son's best friend, an American University student, was asleep, too.

"The dog was making a terrible noise, like a child whinning," recalled Mrs. Sindjelic. It was the third night in a row that Astra had paced and panted down between their upstairs bedrooms as if she sensed danger. Yesterday, the dog went into Sindjelic's bedroom a few minutes before 4 a.m. and woke him up. The Sindjelics were trying to quiet the dog when the bomb exploded.

"I knew it was a bomb the minute it went off," said Sindjelic, his country's acting ambassador during the temporary absence of Yugoslav Ambassador Budimir Loncar. His wife was ready to dash for the stairs, but he tried to hold her back.

"Be quiet," he told her. "Don't go downstairs." Sindjelic was afraid terrorists had planted another bomb, he said later.

But she ignored him and ran downstairs into the acrid cloud of gunpower and debris. "It's a bomb!" she shouted. Their house guest heard her and came out of his bedroom, directly in back of the sitting room that had been devastated by the blast.

Through the smoke, they assessed the damage: Antique wood furniture had been snapped like twigs, the front door was bent off its frame and two layers of brick beneath the picture window had been blown apart. Virtually every window in the huse was broken, several lamps, a silver service and a valuable Indonesian Batik painting had been destroyed.

Sindjelic dialed the police. Then Sindjelic, dressed in a black-and-red silk bathrobe and bedroom slippers, accompanied his wife and house guest, who were also in night clothes, across the street into the yard of their neighbor, George Largess, a retired Navy officer who teaches math at Carodozo High School.

Largess and his wife, Zoe, served the three steaming mugs of instant coffee beneath a towering apple tree, as dozens of police and firemen swarmed onto the quiet, dead-end-street, roped off and cut the darkness with blazing searchlights.

The beleaguered diplomat said he was not afraid. "Why should I be?" he asked. "Things like this happen all the time to my colleagues," Sindjelic, said, referring to terrorist bombings of years past.

But yesterday in the early morning darkness it was simple gratitude, for his neighbor's American hospitality rather than the steely bravado of professional diplomat that was foremost in Sindjelic's mind:

"When you have a problem like this, it is better to have a neighbor [like Largess] than a brother, who might be in another part of the world."