The U.S. ambassador to Argentina, Frank V. Ortiz Jr., in a strongly worded cable to Washington, has criticized House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) and other members of a traveling congressional delegation for allegedly pressuring political leaders in Buenos Aires to condemn Reagan administration policies in Central America.

Ortiz singled out O'Neill, Rep. Marty Russo (D-Ill.) and Rep. Fortney H. (Pete) Stark (D-Calif.) for undercutting his role as the U.S. government's representative in Argentina.

But several representatives, including some who support Reagan's policies, reacted angrily yesterday to the ambassador's charges and suggested that he, not members of the delegation, had been out of diplomatic line.

In the cable, Ortiz stated, "Congressman Russo exceded all bounds in his attacks on the president . . . with Russo stating that [the] president [is] seeking armed confrontation with Nicaragua." The classified cable, which was made available to The Washington Post, added, "Throughout the visit, Russo and Stark joined Speaker O'Neill in attempting to obtain official Argentine condemnation of administration policies."

Russo, reacting to the cable, produced a videotape of the delegation's private meeting with Argentine President Raul Alfonsin in which Ortiz appeared confused about which countries were attempting to negotiate a peace settlement in Central America.

In another section of the tape, Ortiz interrupted a House member's question about finding a peaceful solution in the region and suggested that there was little chance of a negotiated peace with the Marxist Sandinista government in Nicaragua.

One delegation member, who asked not to be named but who supports the president's position on Nicaragua, said yesterday, "The cable is not an accurate portrayal and to try to make an issue of it is going to cost the president votes" next week when Congress takes up a compromise bill to send military aid to the anti-Sandinista contras in Nicaragua and Honduras.

"The ambassador was out of line in trying to inject himself" into the fact-finding sessions between the members of the bipartisan delegation and Argentine officials, the congressman said, adding Ortiz was also "out of line in sending this kind of cable."

This congressman acknowledged that on two occasions during the Argentine visit, two members of the delegation made "highly critical" remarks about the president that "were a bit out of line." But, the congressman said, the give and take of the discussion "did not go anywhere beyond the parameters" of congressional inquiry. At no time, the member said, did O'Neill criticize President Reagan in front of a foreign leader.

Ortiz, a career diplomat with previous postings in Peru and Guatemala, is the highest-ranking Hispanic in the foreign service and is known for his conservative political views. In 1980, the Carter administration transferred Ortiz out of his ambassador's post in Guatemala after he was criticized by human rights groups for not supporting efforts to call attention to the more than 20,000 Guatemalans who had been killed in political violence during the previous 10 years.

When the O'Neill delegation arrived in Buenos Aires two weeks ago, Ortiz accompanied the 14 House members to meetings with Alfonsin and other Argentine officials.

Ortiz complains in his cable that Nicaragua was almost the only subject discussed and that members solicited condemnations of Reagan policies from Argentine officials. "When I saw the speaker off at the airport, I frankly told him [that] in my 35 years of service I had never seen such a performance," Ortiz said in the cable. "To me it seemed to come close to raising constitutional issues of the legislative branch intruding far into the prerogatives of the executive branch."

Despite Ortiz's tone of outrage, his cable clearly indicates that during the meeting between O'Neill and Alfonsin, there was no need to prompt the Argentine president to state his strong view against U.S. policy toward Nicaragua.

The delegation member who supports Reagan said less support was found in Argentina for Reagan policies "than any place else we visited."

Alfonsin told the delegation that Latin American pressures on the Sandinistas were the only way to effectively create a pluralistic democracy in Nicaragua. When Rep. George Miller (D-Calif.) encouraged Alfonsin to use his prestige in Latin America to urge negotiations, Ortiz interrupted to ask Alfonsin whether he knew of any instance where a Marxist-Leninist government had agreed to accept democratic reforms.

Ortiz's remark prompted Rep. Stark to snap, "Mr. Ambassador, the members want to inquire."

O'Neill was not available for comment yesterday. His aide, Christopher Matthews, along with Stark, Miller and Russo arranged a viewing of Russo's videotape.