In a sign of its increasing concern over the situation in emergency-ruled Pakistan, the United States has started making contingency plans in case the turmoil disrupts supply lines to American troops stationed in Afghanistan.

Pentagon spokesman Geoff Morrell said even though the supply lines remained "open", American commanders in Afghanistan are showing "very real" concern since 75 per cent of all supplies, including 40 per cent of all fuel, flow either through or over Pakistan.

"If it becomes necessary to alter our supply lines, we want to make sure we have a backup plan. Clearly, we do not like the situation that we find ourselves in right now," Morrell said, adding he did not know how long it will take to establish an alternate supply route.

The official, however, refused to say whether the move reflected a lack of confidence in President Pervez Musharraf [Images], who is increasingly becoming isolated with most of the political parties and civil society in Pakistan opposing his decision to impose emergency.

"I'm not going to get into whether that reflects ill on President Musharraf� the fact that we're looking at contingency supply lines you believe is a vote of no confidence in President Musharraf, I wouldn't characterise it as anything more than it is," he said.

The Pentagon official also maintained that the US had no immediate concern about the safety of Pakistan's nuclear weapons, saying, "We believe they are under appropriate control".

Answering a question, Morrell said the US was unaware if resources provided to Pakistan for fighting extremists were being diverted by the Musharraf regime for other purposes, while stressing that military aid to its ally will not be reduced.

"We at this point are not stemming the flow of any of our military aid to Pakistan that goes to war on terror operations," Morrell said.

"That's not to say it's not under review, but the flow of that aid has not stopped, due to the fact that we do not want to do anything to imperil our own citizens or the citizens of Pakistan, for that matter."

Revealing that a planned trip last week by the Undersecretary of Defense Eric Edelman to Islamabad was "cancelled or postponed", Morrell said Deputy Secretary of State John Negroponte will soon hold talks with Musharraf.

"Presumably if this (supply line) is an issue, it will be communicated by Ambassador Negroponte on that trip," the Pentagon spokesman said.

Morrell also urged Musharraf to restore the constitution as soon as possible, doff his uniform and hold free and fair elections.

"As you've heard the secretary (of Defence) last week express his concern that the more time General Musharraf spends trying to enforce the emergency rule, the more resources he devotes to that process, the less are available to go after terrorists in his midst and ours," he said.

"So we are very much encouraging of him to get on with taking off his military uniform, holding free and fair elections, and getting back to law-based constitutional rule as quickly as possible."