The State Department is refraining from any comment on an escalating political crisis in Pakistan.

Thousands, perhaps hundreds of thousands, of anti-government protestors are expected to take part in the "Long March" across the country, due to begin Thursday in Karachi and Quetta. The march, coming at a time when President Zardari's popularity is at an all time low, aims to reach Islamabad on Monday.

Pakistan's main opposition leader, former Prime Minister Nawaz Sharif, is in battle mode against Zardari after the Supreme Court barred Sharif and his brother, former Punjab Province Governor Shahbaz Sharif, from contesting elections.

The country-wide opposition movement is united not by a political party, but instead by a common cause — the restoration of the judiciary.

In scenes reminiscent of the unrest of November 2007, Sharif and other political leaders plan to join lawyers to demand that former Chief Justice of the Supreme Court Iftkhar Chaudray be reinstated after being removed by Musharaf. Zardari has left promises to reinstate him unfulfilled.

The 2007 protests led to Musharraf declaring martial law and ultimately to his resignation.

The offices of the Movement for Justice party, led by former cricket star turned parliamentarian Imran Khan, were raided by police Sunday in what Khan told FOX News was a sign of pre-march government intimidation. Khan intends to make a speech, as do Nawaz Sharif and Chaudray, when the march reaches Islamabad.

Tensions are rising, and rumors of terrorist attacks are swirling — particularly following last week's grenade and shooting attack on the visiting Sri Lankan cricket team in broad daylight in Lahore that left eight people dead. That attack is further indication that the country's security situation is deteriorating and a blow to national pride, as cricket is Pakistan's most popular sport.

Zardari is due in Tehran on Wednesday for a regional economic conference. A Pakistani source told FOX News that he is then due in his former home in exile Dubai, and there is a strong possibility he may not return to Pakistan in the short term if tensions continue to rise or perhaps in the longer term if the political situation slides into chaos. During this week's absence, Interior Minister Rehman Malik is essentially in charge.

A question mark remains over how volatile the march will prove and what elements of the Pakistani authorities would deal with mass civil unrest. The police would traditionally deal with clashes, but if the situation deteriorates further, a reluctant army could also become involved and call for the government itself to be replaced. Constitutionally the chairman of the Senate would then become acting president and call elections.

The state department is being unusually silent on the situation. Spokesmen will not yet comment, and there have been no U.S. appeals for calm.

U.S. Ambassador in Islamabad Anne Patterson reportedly met with both Prime Minister Gilani and Shahbaz Shariff in recent days, but the State Department would not confirm. No higher level phone calls have been confirmed either. A State Department official would only say that the anticipated review on Pakistan "is at an advanced stage."

The assistant secretary of state for the region, Richard Boucher, is on leave, and Special Representative Ambassador Richard Holbrooke is in the U.S., but his office could not detail his schedule.