Key outside supporter of the United Progressive Alliance government, the Communist Party of India-Marxist on Wednesday issued a fresh threat, saying that it would pull down the government if it 'falters' on foreign policy and 'succumbs' to US pressure.

"If it falters, we will pull down the government. We cannot afford to be drawn into the strategic tie-ups. We will not permit the government to succumb to the US pressure," party leader Sitaram Yechury said in the Rajya Sabha.

"Although we support the government now, we will be the first to oppose the government if it succumbs to the pressure," he added. He was participating in a discussion on statement made by external affairs minister Pranab Mukherjee on foreign policy-related developments.

The Left parties have strongly opposed the India-United States nuclear deal and given enough hints that they would withdraw support to the government if it went ahead with the deal.

Referring to the Indo-US military exercise including Japan [Images], Australia and Singapore in the region, he said, "It is a clear indication that we are part of a set-up in the leadership of US in the region." He alleged that pressure has been mounted on India to 'divert its foreign policy'.