LUANDA, Angola (CNN) -- Angolan President Jose Eduardo dos Santos on Wednesday rejected international calls for peace talks with the rebel group UNITA, calling rebel leader Jonas Savimbi a liar who has not complied with a 1994 peace accord.

The government "will never again accept the demands from outside the country to give ... one more chance to the liars who have demonstrated that they are unable to accept differences of opinion within the framework of peace and democracy," he said.

Angolan and rebel troops were still fighting Wednesday in the vicinity of the jungle crash site of a U.N.-chartered plane, keeping rescue teams from the downed plane and possible survivors.

The U.N. said it had received no response from the government or from UNITA leaders despite urgent pleas for a temporary cease-fire so rescuers can access the site where the plane went down on Saturday.

Government officials said they had received no such request.

"Normally such a note should be addressed to the Ministry of Foreign Affairs, but we have not received any note ... about this issue," said Deputy Foreign Affairs Minister Sebastiao Isata. "I cannot comment on something that does not exist."

The C-130 transport plane crashed just after takeoff from Huambo with 10 U.N. monitors and four crew members aboard. Searchers located the wreckage on Tuesday and said the plane was relatively intact, building hopes that there were survivors.

U.N. peacekeepers in Angola

Some 7,000 U.N. peacekeepers are in Angola to monitor the 1994 peace accord, signed in Lusaka, Zambia. But government troops began an offensive against rebel strongholds on December 5, saying UNITA had not complied with the agreement.

"The government is just acting in self-defense," Isata said. "If UNITA was disarmed there would be no war."

Isata called on the United Nations to "take very energetic measures to disarm UNITA."

"The U.N. and MONUA (the U.N. Observer Mission in Angola) have to comply with their duties," he said. "They were the ones who were responsible for the demilitarization of UNITA. The war has continued because of negligence of the U.N. and MONUA."

Since it gained independence from Portugal in 1975, Angola has been torn by conflict. Government and rebels signed an earlier peace deal in 1991, but that agreement fell apart in 1992 when UNITA refused to accept its defeat in the country's first democratic elections.