The United States might have refused to admit the ailing shah of Iran last month except for "enormously obnoxious" pressure from former secretary of state Henry A. Kissinger and a few others, longtime diplomat George W. Ball said yesterday.

Ball, an undersecretary of state under Presidents Kennedy and Johnson, said the United States should not have admitted the deposed Shah Mohammad Reza Pahlavi for cancer and gallstone treatments in New York City. The Carter administration, he said, "stood firm on this" until Kissinger and others he did not name began urging officials that the shah be allowed into the country.

"Had it not been for Mr. Kissinger and a few others making themselves enormously obnoxious for the administration, trying to force the shah into this country, maybe we wouldn't even have done it, even for reasons of compassion," Ball said during an interview on "Meet the Press" (NBC, WRC),

Radical Islamic students under the leadership of Ayatollah Ruhollah Khomeini seized the U.S. Embassy in Tehran on Nov. 4 after the shah was allowed into the United States. The students are holding 49 Americans hostage in the embassy; earlier they released 13 American hostages.

Kissinger told reporters at a news conference Saturday in Philadelphia that he had not pressured U.S. officials into letting the shah into the country.

He said an account Saturday in the Boston Globe that he met with Secretary of State Cyrus R. Vance last month and urged him to admit the shah was "totally wrong."

"I strongly support the decision," Kissinger said. "It just so happens I did not bring it about."

Ball said on television yesterday, however, that Kissinger and others had pressed for the shah's admission "from the beginning." News accounts have said that Kissinger and David Rockefeller, board chairman of the Chase Manhattan Bank, were among the prime movers to have the shah come to the United States after he was deposed last January.

Ball, now an investment banker in New York, was appointed by President Carter last December to head an interagency study of the situation at the time in Iran.

He said he found that the shah's political position was hopeless. "He was like Humpty-Dumpty," said Ball. "He couldn't be put back together again."

Ball said he tried to alert the Carter administration and to persuade it to exert pressure on the shah to transfer his power to a broader, democratically selected government. But he said his advice was not followed.

Ball suggested that the current situation in Iran could shift by the beginning of next week after the Iranians hold their Dec. 2 referendum on a proposed new constitution. Approval of the constitution, he said, would install Khomeini "as the supreme head of everything."

Adoption of the new constitution could lead to a softening of the current anti-U.S. position by the Iranians and possibly a moderation in the views of the 79-year-old religious leader as well.