Gunrunner Eugene Hasenfus, pardoned from a 30-year jail term in Nicaragua and carrying the key to his cell, returned to the United States yesterday, thanking God that "I was able to be free and be with my family" for Christmas.

The 45-year-old former Marine, accompanied by his wife Sally, arrived in Miami aboard a commercial flight from Guatemala City shortly after 3 p.m. and then appeared briefly at a news conference, where he refused to talk about his experiences in Nicaragua.

They were to fly on to their home in Marinette, Wis., later yesterday.

"Right now, I am just looking for some time in these special holidays that I was allowed, and thank God I was able to be free and be with my family, and I'm looking for a little private time with them," he said.

He told reporters he couldn't "explain the gratitude in my heart at seeing all of you here and being able to step on American soil again. My great gratitude and appreciation I have to send to many people who have morally helped my family, my wife Sally, my inlaws and myself with cards and letters and phone calls."

He said he was especially pleased to be able to arrive home in time for the holidays and the birthday of his son, who turned 7 yesterday.

He told reporters that he looked forward to "another time when I'll be able to speak with you all at a different time."

He landed in Miami one day after Nicaragua's leftist government freed him in what it called a goodwill gesture to the United States.

Hasenfus said in Guatemala that Nicaraguan Interior Minister Tomas Borge, who oversees the national penal system, had given him the key to his cell at Tipitapa prison, 12 miles east of Managua.

He said he believed the Sandinistas released him as a Christmas gesture. He declined to give his view of the Nicaraguan government, saying, "This will be talked about in time."

He said he was told shortly before noon Wednesday that he was going to be freed.

"Grab your things, you are leaving," he quoted the prison commander as telling him.

He had been turned over in Managua, the Nicaraguan capital, on Wednesday to Sen. Christopher Dodd (D-Conn.) who discussed the Hasenfus case with Nicaraguan President Daniel Ortega the previous day.

Hasenfus and his wife had a candlelight dinner at the home of U.S. Ambassador to Guatemala Alberto M. Piedra where they spent the night, the Advocate newspaper of Stamford, Conn., reported yesterday.

Hasenfus was captured October 6, the day after his plane was shot down while ferrying weapons and supplies to the U.S.-backed Contra rebels in Nicaragua.

Hasenfus was the only survivor when the Sandinistas shot down his plane over southern Nicaragua. He said he was working as a cargo handler on the flight. Two other Americans and a Nicaraguan died in the crash.

After a trial before a People's Tribunal composed of a lawyer, truck driver and laborer, Hasenfus was sentenced last month to 30 years for terrorism and other crimes. He was being held in the Tipitapa prison outside Managua when he was freed.

Ortega told reporters before Hasenfus was released that the pardon also would be a birthday gift for Hasenfus' son Adam. The Hasenfuses also have a daughter, Sarah, 12, and another son, Eugene Jr., 9.

"Let this be a reminder to President Reagan that there are children here that must have birthdays without the threat of death and mutilation," Ortega said.

At Ortega's request, the Nicaraguan National Assembly voted to pardon Hasenfus, a process that took only a few hours from the time it was first announced by the Nicaraguan government radio station.

Dodd, a member of the Senate Foreign Relations Committee traveling in Central America, issued a statement Wednesday saying Hasenfus was released on humanitarian grounds.

"I did not ask that he be pardoned, and there was no quid pro quo for his release," he said. "Mr. Hasenfus' situation was a small part of my conversation with Ortega, perhaps 15 minutes of a 4-and-a-half-hour conversation."

Dodd told ABC's "Good Morning America" yesterday that he accepted at face value the reasons the Sandinistas gave for releasing Hasenfus.

"They said this was the Christmas season, [and that they wanted to] reunite a family.... I think they wanted to demonstrate to people in the United States that they could be humane."

In Washington, the State Department said in a statement: "We are gratified that the Sandinistas have released Hasenfus and that he will be reunited with his family during the Christmas season. However, the handling of this entire incident was orchestrated by the Sandinistas for maximum propaganda effect."