PRETORIA, SOUTH AFRICA, JUNE 26 -- Nine white right-wing leaders warned President Frederik W. de Klerk today that he must hold new elections to show he has white support for negotiations with the "communist" African National Congress or they will seek to stop him by "other means."

"If the government proceeds on this course and does not call an early election, then of course the government is closing the constitutional doors," said Jaap Marais, leader of the Reformed National Party, and spokesman for the group.

"Obviously, people will be considering how to continue the fight with other means," he said.

De Klerk, who is facing mounting right-wing resistance to his reform policies, met for 90 minutes with four Afrikaner right-wing groups not represented in Parliament and actively involved in organizing both armed and political opposition to the de Klerk government.

Among the delegates was Col. Servaas de Wet, a former top police official who now heads the shadowy military wing known as "the commandos" of the Afrikaner Resistance Movement.

Marais said the delegation had asked to meet with de Klerk to convey "the very deep feelings of unrest and insecurity" within the Afrikaner community over his reform polices and negotiations with the ANC and the South African Communist Party.

The growing militancy of extreme right-wing groups was underlined last weekend by bomb explosions at two branch offices of the ruling National Party in the Johannesburg region. While no one has taken responsibility for the bombings, police spokesmen said the use of commercial explosives suggested it was the work of white right-wing groups.

The de Klerk government, in dealing with the white right-wing opposition, has done little to crack down on the proliferation of vigilante commando and armed "neighborhood watch" groups that have sprung up in white communities across South Africa.

Marais said that de Klerk's National Party had never won a mandate in last September's white elections to undertake such policies and that right-wing groups were vehemently opposed to the advent of "communist rule" in South Africa.

"We are convinced that nothing whatsoever will appease the British and American governments unless there is an ANC government in South Africa," Marais said.

Marais said the only point of discussion where there was "a semblance of agreement" between de Klerk and his delegation today was on the issue of seeking protection for "the Afrikaner nation" in negotiations with black nationalist groups.

"He said he was as much concerned about the Afrikaner nation as we were," said Marais, who added that de Klerk had not indicated how he intended to protect their interests.

De Wet, making a rare public appearance, said there were now 10 different Afrikaner groups organizing armed commando units to defend their community. De Wet said he had assured de Klerk that they were not forming a separate secret army in opposition to the South African Defense Force, but intended nonetheless to continue mobilizing recruits in the event that an ANC government comes to power.

De Wet refused to say how many men had joined the commandos, saying, "We don't want the enemy to know what we've got already."