The US Defence Secretary William Cohen said Nato warplanes would now "take the battle to individual units" of Yugoslav forces.

It comes after the US State Department named top Yugoslav military commanders it believed could be indicted for war crimes and crimes against humanity in Kosovo.

James Rubin: "What we're doing is putting them on notice"

Following meetings with Nato Secretary-General Javier Solana and Alliance Supreme Commander General Wesley Clark, William Cohen said the campaign would be "intensified in the coming days and weeks".

He approved additional aircraft for the campaign and said: "...whatever General Clark feels he needs in order to carry out this campaign successfully he will receive."

David Shukman reports: "He is deeply moved and holds one man responsible"

In a BBC interview, Nato Secretary-General Javier Solana said - expressing his personal opinion - that the Yugoslav president, Slobodan Milosevic, should be indited for war crimes.

'World is watching'

The US State Department said it had identified military commanders it believed to be responsible for war crimes based on evidence from intelligence sources and reports from ethnic Albanians escaping Kosovo.

US intelligence sources have been gathering information on atrocities

Spokesman James Rubin said he was naming the officers "as a warning to them that the world is watching" but added that it would be up to an international war crimes tribunal to indict them.

"We're not saying that these individuals are, to our knowledge, directly responsible for war crimes," said Mr Rubin.

"We believe that the police forces and the military forces are conducting war crimes and crimes against humanity, that these are the names - to the best of our knowledge - of the commanders of those units."

Monitoring events

Mr Rubin said any responsibility by President Milosevic would be "a matter for the tribunal, pursuing its evidence wherever it leads."

"We're continuing to monitor events in Kosovo, including changes in command of the Yugoslav military... and will provide this and further information, including additional names, as we can to the prosecutor of the tribunal," he added.

Balkan affairs analyst Dr Kate Hudson told BBC News 24: "If Nato wants to retain the option of negotiating a peace settlement they will have to negotiate with Milosevic and if he is an indicted war criminal it would not be such an easy step to take."

Mr Rubin identified the following commanders:

• Col. Milos Mandic, 252nd Armored Brigade, central Kosovo.
• Maj. Gen. Vladimir Lazarevic, Pristina Corps.
• Col. Mladen Cirkovic, 15th Armored Brigade, Pristina.
• Col. Dragan Zivanovic, 125th Motorized Brigade, Kosovska Mitrovica and Pec.
• Col. Krsman Jelic, 243rd Mechnized Brigade, Ursoevac.
• Col. Bozidar Delic, 549th Motorized Brigade, Prizren and Djakovica
• Col. Radojko Stefanovic, 52nd Mixed Artillery Brigade, Gnjilane
• Col. Milos Djosan, 52nd Light Air Defense Artillery-rocket Regiment, Djakovica.
• Maj. Zeljko Pekovic, 52nd Miliary Police Battalion, Pristina.

Earlier on Wednesday, The International Criminal Tribunal for the former Yugoslavia (ICTY) said it needed more help for its investigations in Kosovo.

Deputy prosecutor Graham Blewitt, said: "We are being tantalised with evidence (from Nato and the allied forces) and then having to go search for it.... We certainly haven't received what we expected."

Mr Blewitt indicated that the ICTY's own investigation teams would be reinforced with other investigators towards the end of the week.