Francisco Aquino, El Salvador's ambassador to the United States, has resigned effective April 1, the Salvadoran Foreign Ministry announced yesterday.

Aquino said here that he notified his government Monday and then spoke with Salvadoran officials by phone Thursday. "They said there would be no problem," Aquino said. "I am not leaving for political reasons. I have very personal reasons."

Aquino, 61, has been ambassador almost one year. He had been president of the International Bank of El Salvador, which was nationalized last March.

"I'm not a man linked to any political party," he said. "I was badly hurt by the nationalization of personal property and I've gotten no compensation. Now, I've worked for the government for a year. It's time I looked out for myself."

Of the tense political situation and violent civil war in El Salvador, Aquino said, "I think their crisis now is not as bad as before. Yes, there are threats from the extreme right now, but the country's military situation, in terms of dealing with the onslaught of weapons from abroad, is improving."

There had been rumors here that Aquino would be asked by his government within the month to leave his post. "Personally Aquino is a good man, and he speaks good English," said one source. "But there is too much criticism of him in El Salvador." The ambassador denied that he was asked to leave.