The threat of NATO air strikes against Yugoslavia grew Tuesday as last-ditch talks on Kosovo failed. Following is a chronology of key events in the crisis since last March:

1998

March 5: Kosovo conflict escalates dramatically with battle in village of Prekaz. Serbia says 20 ethnic Albanians and two Serb police died while Albanians say 50 nationalists massacred; United States ends limited economic concessions made to Yugoslavia in February.

March 22: Kosovo's ethnic Albanians vote for president and parliament. Serbian authorities dismiss polls as illegal.

April 7: Serbian parliament votes 193-4 to hold national referendum to back Belgrade's rejection of outside mediation.

April 23: Serbian referendum opposes Western intervention.

April 29: Contact Group members except Russia agree new sanctions against Belgrade, including freezing of assets abroad.

July 16: Kosovo Albanians inaugurate parliament, elect speaker; Serbian police order legislators to disperse.

Late July: Serbian forces wage offensive to recapture areas controlled by the separatist Kosovo Liberation Army (KLA).

Aug 16: Serbian forces announce capture of last big rebel stronghold, the mountain town of Junik.

Sept 24: NATO issues ultimatum to Yugoslav President Slobodan Milosevic to stop violence in Kosovo or face air strikes.

Oct 1: Series of massacres of Kosovo Albanians by Serbian troops reported. U.N. Security Council condemns killings. United States and Britain urge citizens to leave Yugoslavia.

Oct 2: Defense Secretary William Cohen warns of air attacks within two weeks.

Oct 5: United States says it detects signs of Serbian military withdrawal from Kosovo.

Oct 6: Russia threatens to veto any UN move to authorize air strikes. President Clinton says NATO is prepared to act.

Oct 13: US envoy Richard Holbrooke outlines deal to avert air strikes; NATO gives Milosevic four days to end offensive.

Oct 16: NATO gives Milosevic 10 more days to comply.

Oct 24: U.N. Security Council authorizes deployment of ground and air monitors in and over Kosovo to ensure fighting has ended.

Oct 27: Serbian security forces withdraw en masse; NATO halts immediate threat of air strikes, reserves final verdict.

1999

Jan 9: Violence escalates; Yugoslavs pound ethnic Albanian strongholds after KLA captures eight Yugoslav soldiers.

Jan 16: Bodies of at least 45 ethnic Albanians are discovered at Racak in southern Kosovo. William Walker, US head of international monitors calls it Serb police "massacre."

Jan 18: Yugoslav government orders Walker to leave within 48 hours, but later allows him to stay; UN war crimes prosecutor Louise Arbour refused entry to Kosovo to probe killings.

Jan 29: Six-nation Contact Group meeting in London summons warring Serbs and ethnic Albanians to attend peace talks in Rambouillet, near Paris, by February 6.

Feb 14: Contact Group extends talks until February 20.

Feb 16-17: US mediator Chris Hill tells Milosevic to make concessions or face air strikes. Milosevic opposes deployment of NATO peacekeepers; KLA rejects calls to disarm.

Feb 19: Milosevic declares "We will not give up Kosovo, even if we are bombed," and refuses to see Hill. Western diplomats and aid workers start leaving Serbia.

Feb 23: Major powers say agreement reached on wide autonomy for Kosovo and demand immediate cease-fire. Kosovo Albanians conditionally accept draft accord subject to two-week delay. Serbs accept broad autonomy for Kosovo, but attach conditions. Implementation conference to be held in France from March 15.

Feb 27: Serb troops deploy in force throughout Kosovo; sporadic fighting is reported in the north.

March 1: Milosevic flatly rejects international peacekeepers for Kosovo.

March 2: Hard-line KLA representative Adem Demaci resigns, increasing chances KLA will sign peace deal.

March 11: House of Representatives backs deployment of US troops in Kosovo as part of any NATO peacekeeping force.

March 15: Peace talks resume in Paris.

March 17: Forensic report on the deaths of 40 ethnic Albanians in Racak calls it a "crime against humanity" but refuses to term it a massacre or blame the Serbs.

March 18: Kosovo Albanians sign the international peace deal in Paris but their Yugoslav adversaries boycott the event and Russia refuses to sign as a witness.

March 19: Contact Group adjourns peace talks, warning they will not reopen unless Belgrade accepts the autonomy accord.

March 20: All 1,380 international monitors withdraw from Kosovo, crossing into neighboring Macedonia as the Yugoslav army sends reinforcements into the area.

March 22: Holbrooke arrives in Belgrade on a last-ditch bid to convince Milosevic to accept the accord.

March 23: Serb parliament solidly rejects NATO demands to send peacekeeping troops into Kosovo. Holbrooke ends his mission, saying Milosevic has refused to agree to a plan for autonomy for Kosovo, secured by NATO troops. The failure of diplomacy opens the way for NATO air strikes.