President Agostinho Neto said here today that he is "prepared and desires" to establish diplomatic relations with the United States but cannot dispense with the large Cuban military presence here until South Africa stops attacking his country.

In his first press conference with American journalists and with Sen. George McGovern (D-S.D.) sitting at his side, the Angolan leader said Angola could do nothing about reducing the number of Cuban troops "because we are being daily attacked by the South Frican," who he charged were arming and training antigovernment guerrillas in southern Angola.

As long as the United States continued to make ending the Cuban presence in Angloa a condition for normalizing ties, 'there is nothing we can do but wait," Neto said.

One clear indication of Angola's desire for American diplomatic recognition, however, has been the red carpet treatment McGovern has been getting during his two-day visit.

In addition to meeting for over an hour with Neto and nearly three hours with the Angolan foreign minister, Paulo Jorge, thesenator today was allowed to visit the three Americans, two fo them convicted mercenaries, being held in Angloan jails.

They are Gary Acker, 24, of Sacramento, Calif., and Gustavo Grillo, 32, whose parents live in Tom's River, N.J. Both were captured in northern Angloa in February 1976 while serving with the National Front for the Liberation of Angola, the Westernbacked faction that lost the 1975-76 civil war.

The third American was identified as George Gause, 50, of Arpon Springs, Fla., who was arrested 18 months ago on his farm east of Luanda for being in possession of a rifle and pistol. He has never formally been put on trial and it was the first time he had been allowed a visit by and visiting American official.

McGovern said he had thanked President Neto for letting him visit the American prisoners and had made an appeal to humanitarian considerations regarding their possible release, but would not go into any detail of his discussions about this issue with the Angolan leader.

McGovern, who saw the three individually for about 20 minutes each, said they appeared to be in "reasonably good physical condition," and that Gause was hopeful of being released soon.

Acker is serving a 16-year sentence and Grillo a 30-year term but both told McGovern they were extremely grateful they had not been executed, as Daniel Gearhart of Kensington, Md., was in July 1976.

McGovern has been staying at the presidential guest house while here and it is the first time a group of American foreign correspondents has been allowed into Angola since the mercenaries were tried in June 1976. McGovern is the first member of Congress to visit Angola in two years.

Both steps appear to indicate the Angolan desire to improve its relations with the United States, which has refused to recognize the government of the Cuban-and Soviet-backed Popular Movement for the Liberation of Angola since its victory over two pro-Western factions.

Since the Nixon administration, the United States has indicated that it will not recognize Neto's government until not recognize Neto's government until there is some reduction in the number of Cuban troops in Angola, which State Department estimates put at about 19,000.

McGovern said later the Angolans just could not understand why the U.S. government was withholding recognition because of the Cuban troop issue when it had normal relations with Ethipoia, which has as many or more Cuban soldiers in its country.

McGovern told a press conference here Monday that he thought it was going to take "some concessions" on both sides and further discussion and negotiations before the two countried establish diplomatic ties.

"But I wouldn't be here today if I didn't believe it were possible for us to improve our relations with Angola. I am convinced that it is."

At today's joint press briefing, Neto dismissed as one of the troubles of a young nation the Cabinet shakeup here which has seen the dismissal of his prime minister, Lopo do Nascimiento and three deputy prime ministers as well as several ministers over the past three days.

On the recent reconciliation between Angola and Zaire, which had backed the national front during the civil war, Neto said "everything is going well' and that he looked forward to developing closer economic ties with his northern neighbor.

While the Angolan president said little at his press conference about the future of American companies here, McGobern said Neto had told him in their private meeting that he would welcome seeing more of them invest in Angola.

Gulf Oil Co., which has an offshore field in northern Angola, now provides 80 percent of this country's foreign exchange and a number of other U.S. companies are showing an interest in exploring for oil here.

McGovern is scheduled to leave here for Paris tonight after winding up a three-week tour through Africa that has taken him to Sudan, Tanzania, Mozambique, Rhodesia, South Africa, and Zambia.

The senator has said here that he will seek to become the chairman of the Africa subcommittee of the Senate Foreign Relations Committee.