TRIPOLI, Libya — Two months into the NATO bombing campaign against Moammar Gadhafi's forces, Britain's top military commander has said that the Libyan leader could remain "clinging to power" unless NATO broadened its bombing targets to include the country's infrastructure.

The comments, by Gen. David Richards, came at the end of a week that saw NATO step up its airstrikes, with an accelerated tempo of attacks on the capital, Tripoli. In the predawn hours of Thursday, a volley of heavy bunker-busting bombs that struck Gadhafi's underground command headquarters in the city appeared to have narrowly missed killing the Libyan leader.

Gadhafi's defiant audio message in the wake of that attack, telling NATO he was "in a place where you can't get me," appears to have played its part in galvanizing opinion among NATO commanders, particularly in Britain and France, two nations that have carried the bulk of the bombing campaign.

Britain, in particular, with heavy combat commitments in Afghanistan and mounting costs for the Libyan air campaign straining its military budget, has been concerned that the conflict could be settling into a long-running stalemate.

Under the U.N. Security Council resolution approving the Libyan air campaign, NATO was empowered to use "all necessary means" to protect the country's civilian population from attack by pro-Gadhafi forces, which hold Tripoli and much of western Libya, while rebel forces control much of the country's eastern region. That mandate has been stretched beyond attacks on tanks, artillery and other units engaged in front-line combat with the rebels to a wide range of targets in Tripoli and elsewhere that have been identified by NATO as "command-and-control" centers, including Gadhafi's Tripoli bunker.

But with the war now nearing the end of its fourth month and the two sides skirmishing for gains of a few miles in battle zones spread across hundreds of miles of desert and mountains, there has been growing concern in NATO capitals that the strategy needs a game-changing adjustment that might bring a rebel victory closer.

NATO officials have made no secret of their belief that this would most likely come with attacks that weaken Gadhafi's hold on Tripoli, ideally attacks that spread a sense of despondency among Gadhafi forces and lend an impetus to a rebel underground that has roots in some quarters of the city.

Richards, chief of the defense staff in Britain, spoke in an interview at NATO's southern headquarters in Naples, Italy, which has served as a command center for the attacks. "The vise is closing on Gadhafi, but we need to increase the pressure further through more intense military action," he said in the interview, published in The Sunday Telegraph. "We now have to tighten the vise to demonstrate to Gadhafi that the game is up and he must go."

He added that the bombing campaign, which has involved more than 2,500 sorties since it began March 19, had been "a significant success." But he added: "We need to do more. If we do not up the ante now there is a risk that the conflict could result in Gadhafi clinging to power."

The general suggested NATO should be freed from targeting restraints that have precluded attacking infrastructure targets; other NATO officials have suggested in recent weeks that these could include elements of the electrical power grid in government-held areas, and fuel dumps. And he defended attacks seemingly aimed at Gadhafi himself, saying that "if he was in a command-and-control center that was hit by NATO and he was killed, that would be within the rules."

A tally of NATO attacks given by alliance spokesmen in Brussels gave a measure of how the bombing had already been intensified, with a strong focus on Tripoli. NATO said that alliance aircraft struck 39 "key targets" in and around the capital in the first four days of last week, including the strike Thursday on Gadhafi headquarters in the heavily fortified Bab al-Aziziya compound in south-central Tripoli. The Tripoli targets, NATO said, included seven "command-and-control" centers, compared with only three similar strikes in the 10 days before then.

But the increased tempo of the attacks has shown little sign, so far, of seriously destabilizing Gadhafi's rule. For weeks, there has been a heavily dispirited atmosphere in Tripoli, with many ordinary Libyans seemingly eager to pull Western reporters aside, out of earshot of government minders, to say they yearned for Gadhafi to be ousted. NATO bombing attacks have often been followed by outbreaks of automatic fire in neighborhoods in central Tripoli, apparently started by hit-and-run attacks by elements of the anti-Gadhafi underground.

Airstrikes have also remained intense against pro-Gadhafi forces attacking rebellious cities, with new bombing reported Sunday around the western city of Misrata and another rebel stronghold, Zintan.

At the border with Tunisia, the Tunisian military repelled more than 200 soldiers loyal to Gadhafi as they tried to cross, but no shots were fired, according to TAP, the official Tunisian news agency.

The loyalist forces, aboard roughly 50 four-wheel-drive vehicles, seemed to be seeking to cross into Tunisia some distance from an official border crossing, at Dehiba, where rebel forces hold control, the agency reported. The TAP report could not be independently confirmed.

Scott Sayare contributed reporting from Paris.