Worried at the emerging reports from Pakistan, the United States has announced that it would provide immediate assistance to $8 million for "unexpected and urgent refugee and migration needs" in Pakistan, including through international non-governmental organizations.

Meanwhile, Democratic Senator John Kerry has said the United States must do what it can to "sustain the democracy" in Pakistan.

General David Petraeus, the US military commander for the region, and Richard Holbrooke, the special envoy for Pakistan and Afghanistan, will brief lawmakers Thursday on Pakistan's political crisis, Kerry said, , who chairs the Senate Foreign Relations Committee.

Pakistan's leaders are working very, very hard to try to reach an agreement that will bring elements of the government together in unity and allow them to go forward," said Kerry.

EARLIER REPORT BY PTI:

Amidst deepening political crisis in Pakistan, the United States has conceded that it is a difficult situation in Pakistan but said that Washington supports freedom of speech and expression.

As reports of massive crackdown, arrest and detention of the opposition leaders supporting the march came out, the State Department asserted that it supports freedom of speech, expression and assembly in Pakistan.

State Department's Acting spokesman Robert Wood told media persons at his daily press briefing that the US stand has been that it supports freedom of speech, of expression, and of assembly in Pakistan.

"What we think is important is that the various parties try to resolve their differences within the political system of Pakistan in accordance with its constitution with respect for the rule of law," Wood said.