Angolan President Agostinho Neto yesterday called on the United States to establish diplomatic relations with his government and said Angola was "on the good road" toward a reconciliation with neighboring Zaire.

In a rare press conference, the soft-spoken Angolan leader said, "At this moment we can only hope that the United States wants to establish relations with Angolan. We have no reservations. Everything depends on the United Sttates."

But he added later, Angola is not ready to meet such American preconditions as the withdrawal of Cuban troops from his country in order to obtain U.S. recognition. "They will have to take us as we are and no other way. They cannot oblige us to change. As we are and the way we are, we are prepared at any moment to establish relations with the United States."

This is by far the most explicit appeal for a change in the U.S. government's attitude toward Angola that Neto has ever made publicly.

[In Washington, a State Department source said the United States would decline to establish official ties with Angola until there is "a substantial reduction" in Cuba's military force there.]

[But the source conceded the Neto probably would be unable to reduce the number of Cubans as long as he is beset by opposition guerrilla forces who reportedly control a large chunk of Angolan territory.]

The United States has refused to recognize the Neto government ever since it won in the 1975-76 civil war against two Western-backed nationalist factions with the help of massive Soviet arms and thousands of Cuban combat troops. The Carter administration has been demanding the withdrawal of these troops as a precondition for a normalization of its relations with Angola.

Angola's reconciliation with Zaire which is one of the more significant recent developments in Africa, may help reduce Neto's border problems somewhat.

His public call for U.S. recognition follows talk held quietly earlier this month with U.S. special envoy Donald McHenry, who went to Angola to discuss how to decrease tensions with Zaire.

As a result, high-ranking delegations from the two African countries met last weekend in Brazzaville, Congo, and worked out terms for ending their differences.

Neto, who took the initiative in bringing the two delegations together, also is credited by Western diplomats with playing a crucial role recently in getting militant nationalists to accept a Western peace plan for Nambia.

In a speech Thursday before the annual summit meeting of the Organization of African Unity being held here, Neto sait that "Cuban troops will not leave Angola on my orders so long as the military, politcal and diplomatic aggression persists."

And, he added, the number of Cuban troops "will even increased if need be."

Still Neto was clearly in a conciliatory mood and appeared eager not only to better his relations with the United States but to improve them further with Zaire. As best as reporters here could recollect, it was the first time he had met with the Western press at an international gathering since the end of the civil war.

Neto said he saw no further obstacle to Angola establishing diplomatic relations with Zaire and listed the moves he has taken recently to clear the way for an Angolan-Zairian reconciliation. These included, he said, moving 250,000 Zairian refugees away from the border along Zaire's southern Shaba Province and disarming "thousands" of Lunda rebels involved in the mid-May attack on the Zairian mining city of Kolwezi.

"We took their vehicles and all the other means at their disposal," he said referring to the rebels' arms as well as stolen cars, trucks and household goods taken from Kolwezi. The rebels returned to their camps located in northeastern Angola after retreating upon the arrival of French paratroopers.

Unconfirmed reports circulating here say Angola has also arrested rebel leader Nathaniel Mbumba, whose relations with Neto are said to have never been good. Mbumba's reported arrest was the latest bit of evidence that the rebel standing with the Angola government has sunk to an all-time low.

Neto said Angola has disarmed the rebels as a unilateral move that was not part of a larger agreement in which Zaire would also undertake to halt the military activities of three dissident Angolan groups operating from Zairian territory.

These are the National Union for the Total Independence of Angola (UNITA), the National Front for the Liberation of Angola (FNLA) and the Front for the Liberation of the Enclave of Cabinda (FLEC).

"We are determined to do whatever is necessary . . . and we will take whatever steps we think necessary to improve our relations" with Zaire, he said.

Neto refused to say whether he has met here with Zairian President Mobutu Sese Seko but reliable sources said the two had held a meeting and discussed the recent agreement to take steps to improve their relations.

These include the opening of the Benguela Railroad that Zaire used to depend on to export half or more of its copper ore. It has been closed since late 1975, first because of the civil war in Angola and then because of the Zairian-Angolan feud and UNITA guerrilla attacks on it.

The two countries have also agreed to exchange refugees and set up a four-nation commission under the African organization's auspices to implement the accord and check on military activities along their long common border.

Despite his opening to the West and Zaire, Neto has made it quite clear here that his government has opted for Marxism and is committed to "scientific socialism."

He also indicated at his press conference that a reconciliation with UNITA or the National Front was out of the questions and that their continued existence was an "external problem."

In his summit speech Thursday, he also took a hard line against any attempt by the United States or South Africa to destabilize his government by creating another "Vietnam" for more than 20,000 Cuban troops now stationed in Angola.

He said the number of Cuban troops would even be increased if necessary "so that in a while we will be in a position to answer any aggression against our country, from heaven or hell."

Spelling out the implications of an escalation in the warfare against his government, Neto said Angola would probably become "one of the most militarily strong countries" in southern Africa and make itself more capable of giving "internationalist help" to the nationalists in Nambibia, Rhodesia and South Africa.

In effect, he seemed to be telling the United States in particular that its countinuing hostile attitude toward his government would only make him more determined to build up Angola's military forces and use them elsewhere in southern Africa.