SARAJEVO -- United Nations chiefs pressed ahead with plans for an ambitious new Bosnian cease-fire Friday but the Sarajevo government made clear it was unhappy with a draft agreement that rebel Serbs have approved.


The Bosnian government wants to strengthen the language in the agreement covering a four-month cessation of hostilities under a plan put forward by former U.S. president Jimmy Carter during a freelance peace mission to Bosnia earlier this month.


"The Serbs sent us a very weak document and we are trying to add language that would strengthen the agreement and make it something more than a cease-fire, which we already have," said the Bosnian official, who is familiar with the negotiations.


"The Serbs are trying to go straight from a ceasefire to Geneva for peace talks. We want the UN to help us get a real cessation of hostilities with demilitarization of Sarajevo, routes in and out of the city and monitoring of borders."


Government and Serb officials signed a cease-fire on Dec. 24 and said they would agree a four-month cessation of hostilities by January 1, 1995, followed by peace talks to end the 33-month Bosnian war.


The UN commander in Bosnia, Lieutenant-General Sir Michael Rose, has been shuttling between Sarajevo and the nearby Serb stronghold of Pale all week, trying to narrow differences between the two sides on the planned cessation of hostilities.


After four hours of talks with the Moslem-led government in Sarajevo on Friday, Rose went to Pale to meet Bosnian Serb leader Radovan Karadzic and the Serb military commander, General Ratko Mladic.


"We are still working on the agreement, the basis for which we already have," Rose said in Pale. "We are just looking at some of the final details, and I am very hopeful we'll finish it by tomorrow."


The Serbs are believed to favor a simple agreement with few changes from the interim cease-fire already signed.


The United Nations pledged to make efforts to bring the Croatian Serbs, who are not a party to the truce and who have been attacking the Bihac enclave, into the cease-fire process.


General Bertrand de Lapresle, the UN military commander in former Yugoslavia, hopes to meet rebel Croatian Serbs in their headquarters at Knin, about 90 kilometers south of Bihac.


Major Herve Gourmelon, a UN military spokesman, said there had been 26 confirmed cease-fire violations across Bosnia over the past 24 hours, six determined to be of joint responsibility, four the fault of the Bosnian government army and 16 assessed as the fault of the Bosnian Serb army.