THE HAGUE, August 29, 2008 (AFP) - Bosnian Serb wartime leader Radovan Karadzic refused to enter a plea before a UN war crimes court Friday, attacking the tribunal's independence and labelling it 'a court of NATO'.

An automatic not guilty plea was entered on his behalf as Karadzic made his second appearance before the International Criminal Tribunal for the former Yugoslavia (ICTY) since his arrest in Belgrade last month.

The 63-year-old faces 11 charges of genocide, war crimes and crimes against humanity, notably for the 44-month siege of Sarajevo that left 10,000 dead and the July 1995 massacre of around 8,000 Muslim men and boys in Srebrenica.

'This court is representing itself falsely as a court of the international community where it is in fact a court of NATO,' Karadzic said, claiming the transatlantic alliance was out 'to liquidate me'.

NATO air raids were instrumental in halting the conflict in Bosnia in which more than 100,000 people died and the alliance went on to command a multi-national peacekeeping force in the former Yugoslav republic.

When Karadzic refused to plead, judge Iain Bonomy entered a not-guilty plea on his behalf as tribunal rules dictate.

'I would rather hear you say that (not guilty) at the end of the trial than at the beginning,' quipped Karadzic, wearing a dark suit and red tie and giving off an indifferent air throughout his brief appearance.

Karadzic, who is accused in the 'ethnic cleansing' of non-Serb Muslims and Croats during the 1992-95 war in Bosnia-Hercegovina, opted at his first ICTY appearance on July 31 to delay entering a plea.

Like then, he had no lawyers present Friday, explaining that he would put together 'a team of associates' to assist him in time for the prosecution's filing of an amended indictment.

Alan Tieger, for the prosecution, told the court the new charge sheet should be filed by the last week of September, saying investigators were in the process of 'reviewing a vast volume of material'.

Judge Bonomy expressed surprise that the prosecution had waited until Karadzic's arrest to start this review, and urged it to make haste.

Karadzic, dubbed the 'Butcher of Bosnia' by some media, was arrested six weeks ago on a Belgrade bus posing as a doctor of alternative medicine called Dragan Dabic -- complete with large glasses and big white beard.

In his submissions to the court so far, Karadzic has challenged the legality of his trial and urged the UN court to order evidence from former US diplomat Richard Holbrooke about an alleged secret deal.

Declining to enter a plea immediately, he claimed Holbrooke had promised him at the end of Bosnia's bloody war that he would not face prosecution if he disappeared from the public eye.

But Holbrooke, the architect of the Dayton peace agreement that ended the war, denied cutting such a deal and described Karadzic as the 'intellectual architect' behind an ideology of racial hatred in former Yugoslavia.

'Of all the evil men of the Balkans, he is the worst,' he said.

If convicted, Karadzic faces life imprisonment. His trial is not due to start for several months.

His ally, former Bosnian Serb military commander Ratko Mladic, 66, remains on the run, as does Goran Hadzic, a 49-year-old former rebel leader wanted for Croatian war crimes.

The extent of Serbia's cooperation with the ICTY is a key condition for sealing closer ties with the European Union.

Karadzic's next appearance will be on September 17 when the groundwork for an eventual trial will begin to be laid.