Mitch Snyder, the militant anarchoChristian activist who led a nine-day takeover of the National Visitor Center by homeless "street people" earlier this month, today begins what he says may be a fast to the death to pressure a wealthy Roman Catholic church in Georgetown to give more money to the poor.

A member of the radical Community for Creative Non-violence, Snyder said he will take no food or liquid until Holy Trinity Church, on 36th Street between N and O street s NW, agrees to divert a portion of its $400,000 building improvement fund to the poor and homeless.

"Either Holy Trinity is going to change its way, or I'm going to be dead," said Snyder in an interview last week.

He said his threat is real. He has rejected appeals by several friends who abandon the fast and says he has taken measures to prevent authorities from intervening.

Holy Trinity church and parish officials so far have refused to bow to Snyder's demands in what has become an escalating, almost year-long feud with CCNV.

The officials say Holy Trinity contributes amply to the poor through various channels, and the $400,000 in church repair funds is essential for safety, maintenance and "appropriate worship" in the aging, white columned building.

Many of the city's most influential Catholic business and political figures, including Health, Education and Welfare Secretary Joseph Califano, are members of Holy Trinity.

Holy Trinity's confrontation with CCNV comes ironically after the church's pastor, the Rev. James M. English, suggested in a sermon last spring that CCNV would be a suitable conduit for parishioners to contribute to the poor.

After a brief informal alliance, things turned sour when the parish council announced plans to raise $350,000 in building restoration funds, plus another $50,000 to repair the church's organ.

CCNV, led primarily by Snyder, suggested that a porton of the restoration money be diverted to the poor. The council would not budge. CCNV ACTIVISTS BEGAN APPLYING MORE PRESSURE FIRST LEAFLETING PARISHIONERS AND STANDING IN SILENCE DURING CHURCH SERVICES AND LATER CONDUCTING A 42-DAY WATER-ONLY FAST.

IN EARLY SEPTEMBER THE FAST ENDED WHEN THE COUNCIL AGREED TO RECONSIDER THE BUILDING IMPROVEMENT PROGRAM. THE COUNCIL VOTED LATER HOWEVER TO UPHOLD THE FULL $400,000 IMPROVEMENT PROGRAM. SHORTLY THEREAFTER, SNYDER ANNOUNCED HIS INTENTION TO BEGIN A TOTAL FAST.

THE PARISH COUNCIL, IN A LETTER TO THE 1,429 REGISTERED FAMILIES IN THE PARISH, SAID THE $400,000 IS "LIMITED AND RESTRAINED" AND "PROPORTIONATE WITH THE GENUINE NEEDS OF PHYSICAL SAFETY, MAINTENANCE AND WORSHIP."

THE REV. MICHAEL DOODY, AN ASSISTANT PASTOR AT HOLY TRINITY, SAID YESTERDAY THE MONEY IS NEEDED FOR HEATING AND "AIR HANDLING" EQUIPMENT, STRENGTHENING OF THE BALCONY, CORRECTION OF EXISTS, REDESIGN OF THE ALTAR, CONSTRUCTION OF A NEW SACRISTY AND REBUILDING OF FLOORS AND RAMPS FOR THE HANDICAPPED. THE CHURCH ORGAN, WHICH WAS THE ORIGINAL ORGAN IN THE LIBRARY OF CONGRESS, DOODY SAID, NEEDS EXTENSIVE REPAIRS, TOTALLING $50,000.

SNYDER'S FAST IS THE LATEST IN A SERIES OF DRAMATIC ACTIONS BY THE 35-YEAR-OLD ACTIVIST THAT HAVE EARNED HIM A REPUTATION AS A CHAMPION OF THE POOR AND AMONG HIS SUPPORTERS AND AS A MEDIA MANIPULATOR AND STUNT MAN AMONG HIS DETRACTORS.

A FIERY, INTENSE MAN WHO JOINED THE ANTI-VIETNAM WAR MOVEMENT WHILE IN PRISON IN THE EARLY 1970S AFTER AN OFF-AND-ON CAREER AS A PETTY THIEF AND BAD CHECK ARTIST, SNYDER SAYS HIS TOTAL FAST IS NO STUNT.

"HUMAN BEINGS ARE DYING FROM STARVATION AND HOMELESSNESS," HE SAYS, "WHILE (HOLY TRINITY) HAS RESOURCES AVAILABLE TO STOP IT BUT INSTEAD IS USEING THOSE RESOURCES FOR ITS OWN NEEDS. BY MY FASTING, WE ARE CREATING A WINDOW ONTO THAT REALITY.

SNYDER SAID HE WILL CONDUCT AT LEAST THE INITIAL PHASE OF HIS FAST FROM THE LARGE RAMBLING COMMUNAL HOUSE AT 1345 EUCLID ST. NW, just off the 14th Street riot corridor where he lives with nine other CCNV members

If he falls unconscious in advance stages of the fast, he said, CCNV members will remove him to an undisclosed location to prevent authorities from intervening.

"I figure 10 or 11 days maximum," Snyder said. Supporters in the Euclid Street house say they are aware of possible legal implications in their actions but have accepted Snyder's decision.

Dr. Henry L. Taylor, professor of physiological hygiene at the University of Minnesota Medical School and an authority on starvation, said in a telephone interview yesterday tha a man of Snyder's physique and age could live "maybe 12 to 20 days" withou foodand water.

In recent days, several friends and acquaintances have visted or called the Euclid Street house, some of them attempting to stop Snyder.

The Rev. Richard McSorley, a Jesuit theology professor at Georgetown University and a CCNV member himself, has called Snyder's action "suicidal."

Philip F. Berrigan, a former priest and Vietnam war resister whom Snyder met in federal prison eight years ago, visited Snyder Friday but, according to Snyder, did not discourage the fast.

In a lengthy interview, the shaggy-haired Snyder acknowledged there is a slight chance he might not go through with the death threat. "My conscience says I must do this now," he said, "The voice of my conscience is stronger than any other voice in me at the momemt . . . I'm not saying it may not wealen later on."

Several persons who have been close to Snyder in recent years said privately they feel his action is arrogant and inconsistent with Christian values and that he he has created an unhealty cult-like atmosphere among his supporters in the Euclid Street house.

"Yeah, I know, a lot of people think I'm a suicidal maniac and I just want to get my name in the paper," Snyder said. ". . . But if I die, it won't be suicide. Holy Trinity will have to let me die, and I will just be an example of the other people they are letting die."

Snyder is no newcomer to preotest actions. He has been arrested at least 19 times in Washington since 1972, poured blood on South Vietnamese government documents and leaped over the White House fence.

Born in Brooklyn, N.Y., Snyder said he did not become "politicized" until 1970 when he joined the radical Catholic peace movement after meeting Philip Berrigan and Philip's brother, Dan, in prison.

Snyder was in federal prison in Danbury, Conn., not for political protest actions, but for interstate auto theft ("a bum rap," he says). Prison records show he served 26 months after being convicted of the charge in California in 1970. He also used the alias Mitchell Snyder Peters, according to the records.

Before that, he acknowledges, he was arrested several times for forging checks while he worked intermittently as a management consultant in the New York area.

"As a kid I was also arrested maybe 10 times," he said, "you know, for things like breaking open parking meters . . . I wasn't exactly as pure as the driven snow."

Snyder, whose parents were divorced when he was 9, married at the age of 19, had two children and then obtained a divorce himself.

Father Doody at Holy Trinity says Snyder is simply wrong in saying the church does not help the poor. "We contribute several thousand dollars each year directly to the poor," he said, "and just this fall we gave $50,000 in clothing . . . Many of our members also give to charity through other conduits."

"It is strange that he would pick Christmas Eve, the night Jesus Christ brings his own life to the people of the world, to begin to take his own life," Father Doody said.

". . . If he decides to die, I'll be very unhappy, but I will not feel guilty."