Secretary of State Rice will make the first visit to Libya by an American secretary of state in half a century, in a sign of improving relations with the North African nation once branded a state sponsor of terrorism, envoy Ahmed Gebreel of the Libyan mission to the United Nations said yesterday.

Ms. Rice, who is seeking ways to strengthen ties with the holder of Africa’s largest oil reserves, will travel to Libya in the second half of October, Mr. Gebreel said in a telephone interview. John Foster Dulles, who served President Eisenhower, was the last secretary of state to visit Libya, in 1953.

“We are happy with this announcement,” Mr. Gebreel said. He said the trip resulted from an agreement between Libyan officials and American envoy David Welch, who was in Tripoli this week. “It is a sign of improved relations with the U.S.,” he said.

The visit by Ms. Rice will be a milestone in mending ties with the Libyan leader, Muammar Gadhafi, after the American government restored full diplomatic ties with his government in 2006. The American government also removed the country from a list of state sponsors of terrorism.

The renewal of relations came after Libya took two major steps: giving up its chemical- and nuclear-weapons development programs, and agreeing to pay compensation to families of the 270 people who died in the Libyanlinked 1988 bombing of Pan Am Flight 103 over Lockerbie, Scotland.

Colonel Gadhafi, who came to power in a 1969 coup, declined to meet with Ms. Rice’s deputy, John Negroponte, during his visit to Libya in April.

State Department spokesman Gonzalo Gallegos yesterday declined to confirm Ms. Rice’s visit to Libya and said that “at the appropriate time, you will see an announcement on that trip from my office.”

Ms. Rice last month told American government-funded Radio Sawa, which broadcasts in Arab countries, that she hoped to visit Libya soon.

“Libya made an important strategic decision to get rid of its weapons of mass destruction,” Ms. Rice said in the Radio Sawa interview. “As a result, it has put itself on a path that is leading to investment in Libya by western companies which could not invest there before.”

The American government is trying to widen access to African oil sources and lessen its dependence on the Persian Gulf. Oil companies such as Irving, Texas-based Exxon Mobil Corp. and San Ramon, Calif.-based Chevron Corp. returned to Libya in 2005 after the American government lifted economic sanctions.

Libya wants its oil production capacity to rise by 40% to 3 million barrels a day by 2013, according to a report by the U.S. Energy Department. The country also is seeking to expand natural gas production.

An impediment to deeper ties with America vanished last month when Colonel Gadhafi agreed to free five Bulgarian nurses and a Palestinian Arab doctor who faced the death penalty on charges of infecting Libyan children with HIV. In return, Bulgaria waived $57 million of Soviet-era Libyan debt, and the European Union pledged to restore normal ties and set up an AIDS treatment hospital in Libya.