THE HAGUE, Netherlands - Ratko Mladic, who will appear in public Friday for the first time since his arrest when he goes before a war crimes judge, was "extremely co-operative" when finally taken into UN custody after 16 years as a fugitive, a court official Wednesday.

John Hocking, the registrar of the Yugoslav war crimes tribunal, said the wartime Bosnian Serb military commander understood him clearly when Hocking spoke to him Tuesday night, shortly after Mladic was extradited from Belgrade in a Serbian government business jet.

Hocking, the tribunal's senior administrative official, described the rules and regulations of the detention block that will be the ex-general's home until the end of his trial on charges of genocide and orchestrating Serb atrocities throughout the Bosnian war.

Hocking said a doctor who examined the 69-year-old Mladic saw no medical problems to prevent him being taken into the tribunal's detention unit but declined to provide details about Mladic's health, citing privacy concerns.

The descriptions of Mladic's health and powers of concentration appear to be at odds with those of Mladic's Belgrade lawyer, who has said the ex-general is too weak mentally and physically to face a complex and lengthy war crimes trial. Mladic's family says he has suffered at least two strokes while on the run.

Mladic will appear in court for the first time Friday morning when a judge will ask him to confirm his identity and give him the chance to enter pleas to the 11 charges of genocide, war crimes and crimes against humanity.

Like his old ally and political boss Radovan Karadzic three years ago, Mladic may decline to enter pleas at his first appearance, instead opting to delay a formal response by up to a month.

Tribunal Chief Prosecutor Serge Brammertz praised Serbia's pro-Western President Boris Tadic for having Mladic arrested, but also rued how long it took to detain Europe's most-wanted war crimes fugitive, who was first indicted in 1995 while war was still raging around him.

"Sixteen years is a long time to wait for justice," Brammertz told reporters at the court. "It has happened very late, but not too late."

Brammertz suggested it is unlikely he will seek to try Mladic together with Karadzic, but he did not completely rule out rejoining their cases.

"I am not saying at all this is a likely possibility, but it is at least a theoretical one," he said.

Karadzic, who was president of the self-declared Bosnian Serb republic, was arrested in 2008 and has already been on trial for 18 months on the 11 charges that are all but identical to the allegations against Mladic. The two were originally indicted together, but their cases were split after Karadzic's arrest.

Both men are accused of providing political and military leadership to Serb forces responsible for atrocities ranging from ethnic cleansing campaigns against non-Serbs, to the deadly sniping and shelling campaigns during the four-year siege of Sarajevo, to the war's bloody climax -- the 1995 slaughter of 8,000 Muslim men and boys in Srebrenica, Europe's worst massacre since the Second World War.

Mladic "was the most powerful military figure in Bosnia during the war and he is charged with crimes that shocked the conscience of the international community ... and symbolize the brutality of the war in Bosnia," Brammertz said.

The 1992-95 Bosnian war left about 100,000 people dead and forced 1.8 million to flee their homes.

Hocking said he discussed with Mladic how he would mount his defense against the charges, but said Mladic has not yet indicated his plans.

Several high-profile leaders prosecuted at the tribunal, including Karadzic and former Yugoslav President Slobodan Milosevic, have acted as their own defense attorneys and used their trials as platforms to spread their political message.

Hocking said it has not yet been decided where Mladic will stay in the detention unit, which has several wings. Detainees are free to roam their wings for much of the day and interact with one another before being locked at night in their one-man cells, equipped with televisions and toilets.

Hocking said Mladic was not on any kind of suicide watch, but was being kept in isolation for the first few days of his detention as he adjusts to life behind bars.

Mladic was captured Thursday at the home of a relative in a Serbian village. Judges in Belgrade rejected his appeal to delay his transfer on grounds of ill health, and the Serbian justice minister authorized his handover to UN officials in The Hague.

Justice Minister Snezana Malovic said the handover marked the fulfillment of Serbia's "international and moral obligation." Serbia had been told it needed to capture Mladic before it could be considered a candidate for membership in the European Union.

Of the 161 suspects indicted by the UN court since its establishment in 1993, only one remains on the run -- Goran Hadzic, a leader of rebel Serbs in Croatia.