The outgoing NATO chief pulled no punches as he described Bosnia's defence structures as "schizophrenic" and warned the country that its integration into Europe depended on the apprehension of fugitive war criminals.

He also told Serbia that it had a "duty" to arrest top war crimes suspect Ratko Mladic, and reminded Croatia's nationalists, who won a general election on Sunday, that extremism had no place in the region.

Robertson will step down as NATO chief in January but thousands of alliance troops will remain on duty in Bosnia and the southern Serbian province of Kosovo after he is gone.

Robertson applauded the peacekeepers' efforts to hunt fugitve war crimes suspects like Radovan Karadzic, the former Bosnian Serb political leader who is wanted by the UN tribunal at The Hague.

"Their support networks are being weakened, their bank accounts are being blocked, their freedom of movement has been limited. Slowly but steadily the noose around them is tightening," he wrote in a letter to Sarajevo's Dnevni Avaz daily.

Without speaking directly to the Serb authorities, he said Bosnia had to do more to bring war criminals to justice and cooperate with the UN tribunal.

"The fact that (war crimes suspects) are at large slows your way toward Europe. NATO and the EU want Bosnia as a partner, and possibly as a member, but only as a member that shares our values," he said.

Robertson told a press conference after meeting senior Bosnian and international officials that NATO "will not rest" until all war crimes suspects are apprehended.

On military reform, he said Bosnia's two armies -- one for the Serbs and one for the Muslim-Croat Federation -- were "politicaly divided, economically exhausting and militarily useless."

"No country is able to maintain this kind of defence schizophrenia," he wrote in the newspaper, warning that the country could not join NATO until its defence structures were sorted out.

Bosnia was divided into two entities -- the Serb-run Republika Srpska and the Muslim-Croat Federation -- after the brutal inter-ethnic war that cost more than 200,000 lives in the 1990s.

NATO airstrikes against Bosnian Serb forces helped end the war in 1995 and some 12,000 NATO-led troops are still needed to ensure the country's stability, although their numbers are expected to be cut to around 7,000 next year.

Roberston's Balkan trip began late Wednesday in the Serbian capital Belgrade, a city bombed by alliance jets only four years ago as the West sought to drive Yugoslav forces, under then-president Slobodan Milosevic, out of Kosovo.

The first NATO chief to visit Belgrade since the 1999 bombing, Robertson said Serbia was now being "welcomed by all the Euro-Atlantic community."

But he said the reformist authorities who sent Milosevic to The Hague in 2001 also had a "duty and obligation" to hand over former Bosnian Serb military chief Mladic.

"There are undoubtedly people in Serbia who know where Mladic is," Robertson said after talks with Serbia and Montenegro Foreign Minister Goran Svilanovic, despite Belgrade's repeated claims that Mladic is not in Serbia.

The former British defence secretary also warned the nationalist Croatian Democratic Union party, which won weekend elections, that nationalism had no future in the region.

"We will say to the new government of Croatia that nationalism and extremism are a thing of the Balkan past and have no place in the Balkans' future," he said.

WAR.WIRE