NATO's bombing campaign in Libya has significantly degraded veteran leader Muammar Gaddafi's military power, the alliance's Secretary General Anders Fogh Rasmussen said on Thursday.

"We have significantly degraded Gaddafi's war machine and now we see the results -- the opposition has gained ground," Rasmussen said after talks in the Slovak capital Bratislava with President Ivan Gasparovic

"The Gaddafi regime is more and more isolated every day," the NATO chief added.

"We will keep a strong military pressure on the Gaddafi regime and I'm confident that a combination of a strong military pressure and increased political pressure and support for the opposition will eventually lead to collapse of the regime".

With almost daily bombardments by NATO jets acting under a UN mandate to enforce a no-fly zone and protect civilians, Gaddafi forces have lost control of vast swathes of the east of the country to anti-regime rebels.

But on Thursday, United Nations Secretary General Ban Ki-moon warned the humanitarian crisis in Libya was worsening amid failed attempts to secure a ceasefire.