Islamabad, Aug 22 (IANS): The US Thursday rejected Pakistan Tehreek-i-Insaf (PTI) chief Imran Khan's comment that Washington was interfering in the country's affairs.

The US embassy in Islamabad said that it is not mediating between the Pakistani government and the opposition parties, who are protesting in Islamabad to seek resignation of Prime Minister Nawaz Sharif, Xinhua reported.

The embassy said that Washington will oppose any "extra-constitutional change to the political system" in Pakistan.

Imran Khan, who has been leading his supporters in anti-government sit-ins outside the parliament building for a week, angrily reacted to Washington's stance and described it as interference in the country's affairs.

he claims that the last year's elections had been "rigged" and that fresh elections be held.

The government, however, dismissed the charges as false and has formed a judicial commission to investigate the alleged vote fraud.

A religious leader and Pakistan Awami Tehreek (PAT) chief Tahir ul Qadri has also gathered his thousands of supporters in Islamabad.

Sharif and his party, Pakistan Muslim League-Nawaz, has rejected calls for the government's resignation.