Thirty-three Jesuit priests, facing a rightist terrorist group's threat to kill them beginning Thursday if they do not leave El Salvador, have decided to stay in this small nation."

We will all stay until we are either all killed or expelled," the Rev. Cesar Jerez, head of the Catholic order in Central America said here. He alluded not only to the terrorists' theat but also to the fact that the military-dominated government here has expelled 15 priests, seven of them Jesuits, in the past four months for alleged leftist activity.

The terrorists' execution deadline, issued June 20 coincides with the beginning of U.S. congressional hearings Thurday in the House Subcommittee on International Organizations on the human-rights situation in El Salvador.

With the deadline at hard, armed polxe and unarmed parishioners are guarding the threatened priests.

Events here have coused rising concern in the American Catholic community, and following calls from Notre Dame University president Theodore Hesburgh and the Rev. Timothy S. Healy, president of Georgetown University, Secretary of State Cyrus Vance met with church leaders July 8 in Washington.

The death threats, made by a group calling themselves the White Warriors' Union, gave the priests, most of whom are foreigner 30 days to leave the country or face "immediate and sysematic" execution. The terroist group has charged in communiques that the Jesuits are involved with leftist subversives here.

While there are more than 200 Catholic priests in El Salvador, the small Jesuit community is considered the most militant.

Mary sources believe that the White Warriors' union is linked with goverment security forces and made up of retired milatary officers.

Monday Wl Salvador's president, Gen. Carlos Humberto Romero. condemned growing violene in the coutry "wherever it comes from." It was the first statement he has made acknowledging the existtence of a left right terriorist battle here that has taken the lives of two priests, the foreign minister and a former president this year.

Yesterday the Defense Ministry announced that it would investigate such crimes without distinguishing as to political ideologies, religious creed or economic condition."

In a Washington briefing today, the State Department praised Romero's government for its attempts to calm the situation.

A source close to the government said it fears that if the rightists don't assassinate a priest, leftist guerrillas will. "It is a golden opportunity" he said, because the rightists and hence the government will be blamed.

El Salvador's troubles stem from unequal land distribution that has placed most economic power in the hands of a small wealthy oligarchy. This is the smallest but most crowded Central American state, with a primarily rural population of more than 4 million. Sixty per cent of the farmland is owned by 4 per cent of the people.

The situation became explosive in the past year with the appearance of leftist guerrilla groups that the government alleges are trained and directed by international Communists.

At the same time, the emergence of peasant-based rural organizations and militant support of the poor by the Catholic hierarchy here have led to government suspicions that the church, the peasant movement and the guerrillas are one and the same.

The opposition charges that presidential elections held in March were a fraud, and demonstrations led to clashes with the police and army in which eight people were killed, according to government figures. The opposition said 100 died.

A U.S. congressional hearing at the time, on the alleged election fraud as a possible human rights violation, is believed to have set a precedent.

The battle here escalated quickly. March 12 a Jesuit priest was shot and killed by unknown assassins. Mauricio Borgonove, El Salvador's foreign minister, was kidnaped in April and subsequently murdered. The Popular Liberation Army, a leftist guerrilla group claimed responsibility.

A few days after Borgonovo's body was found an activist priest, a non-Jesuit, was killed by masked gunmen in his San Salvador home. That murder was claimed by the Writer Warriors' Union.

In late may, police and army forces blockaded the town of Aguilares in a search for leftist terrorists. Although reports of the incident remain incomplete, several people were killed and at least one priest has charged that he was imprisoned and tortrured.

That priest will testify at Thursday's hearings in Washington, as will Ignacio Lozano, the former U.S. ambassador to El Salvador who left the country in warly June.An outspoken human-rights advocade, Lozano was widely disliked by the government and business interests here.

Last spring, El Salvador joined five other Latin American countries in refusing all U.S, military aid for 1978 on the ground that U.S. human-rights policy is interference [The Salvadoran embassy , issued a statement saying it supports protection of human rights but "denies to any country of the world, regardless how powerfull it may be, the right to intervene in its internal affairs under the pretext of protecting human right.]