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.

The United States and NATO allies on Monday increased the number of surveillance flights over Libya, while Britain and France said they had also begun drafting a U.N. resolution that could establish a no-fly zone.

Analysts at the IISS said that, while Libya's opposition lacks logistical support and air power, they are likely to become increasingly organized if the current conflict is protracted.

"The longer this goes on the greater the chances of the rebels increasing their combat capability, and the more chance there is for sanctions to bite," said retired British Army Brigadier Ben Barry, of the institute.

Much of Libya's regular army still under Gadhafi's control is poorly equipped, lacks a coherent command structure and is probably suffering from waning morale, he said.

Barry said that though there are better equipped elite forces around Tripoli, they didn't appear to have the capability to contain protests in the capital and simultaneously join offensives elsewhere. "Using these troops outside of Tripoli could loosen his grip there," he told reporters.

Hague said Britain believed neither side had "the immediate power to overthrow the other."

The institute estimated that as of November, Libya had 76,000 active troops and 40,000 militia fighter available as a reserve force. Many of those forces had been based in eastern Libya and sided with the opposition, with elite troops and parts of the air force allied with loyalists closer to Tripoli, Barry said.

In its annual report, the institute said Europe was feeling the effect of reduced defense spending imposed by constraints on national budgets. The U.S. is also seeking military efficiency savings.

"In other regions _ notably Asia and the Middle East _ military spending and arms acquisitions are booming. There is persuasive evidence that a global redistribution of military power is under way," said the institute's chief executive John Chipman.

It also noted the emergence of unlikely centers of expertise in cyber warfare, including Singapore and Switzerland. "The barriers to entry are extremely low," said Nigel Inkster, the institute's director of transnational threats and former assistant chief of Britain's MI6 overseas spy agency.

Inkster also warned that the public may have unrealisitic expectations about the use of drone strikes to tackle terrorists targets along the Afghanistan-Pakistan border.

The use of unmanned drones against militant targets made "counterterrorism look like a game of Pac-Man," when it actually required intensive work on the ground and strong human intelligence sources.

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International Institute for Strategic Studies: http://www.iiss.org/