A no-fly zone over Libya would likely have a limited impact on Moammar Gadhafi's offensives against rebel forces and civilians, military experts said Tuesday, as pressure appeared to be intensifying for restrictions.

Launching its annual report on international military might, the International Institute for Strategic Studies said the use of jets by Gadhafi loyalists appeared to pose less of a threat than the deployment of attack helicopters — which can get around flight prohibitions because they are harder to detect.

The report also warned that defense budget cuts in the West over the last year had accelerated a shift in military powers toward emerging countries in Asia and the Middle East.

British Foreign Secretary William Hague said Tuesday that contingency work is being carried out by Britain and France on a potential United Nations Security Council resolution that would sanction a no-fly zone over Libya.

"There must be a demonstrable need that is accepted broadly by the international community, as well as the strong international support that would come from that," Hague said following talks with Palestinian President Mahmoud Abbas.

Abbas said the Arab League would discuss the prospects of a no-fly zone being imposed at talks this weekend.

Douglas Barrie, military aerospace analyst at the institute, said Gadhafi has around 300 combat aircraft, but that far fewer are likely to be operational and that the leader appeared increasingly reliant on around 35 attack helicopters.

Because they are far smaller and slower moving than jets, it means traditional methods used to enforce a no-fly zone could fail to catch them, he said. Some radar can struggle to distinguish between a helicopter and a fast-moving car or truck, for instance.

U.S. Defense Secretary Robert Gates has suggested a no-fly zone would require an attack on Libya's air defenses.

Barrie said that would not necessarily be required, and that Gadhafi's regime was poorly equipped in any case. "It's not a risk free proposition, but the Soviet-era kit that the Libyans are equipped with is not state of the art," he said.