US Treasury announced on Friday that it has imposed sanctions on Iran's petrochemical industry, including its largest petrochemical holding group, accusing them of supporting Iran's Islamic Revolutionary Guard Corps (IRGC) financially.

The new sanctions blacklisted Persian Gulf Petrochemical Industries Company (PGPIC) and its big network of 39 subsidiary petrochemical companies and foreign-based sales agents, said the Treasury in a statement.

According to the Treasury, PGPIC and its group of subsidiary petrochemical companies hold 40 percent of Iran's total petrochemical production capacity and are responsible for 50 percent of Iran's total petrochemical exports.

Over the recent weeks, Washington has ratcheted up pressure against Tehran with a series of sanctions, designations and military threats.

Iranian authorities have stressed that Tehran would not sit for negotiations under Washington's threats or sanction pressures.

Amid escalating tension, US Secretary of State Mike Pompeo said in Switzerland on Sunday that the United States is ready for unconditional talks with Iran, a gesture dismissed by Iran's Foreign Ministry as merely "wordplay."

The United States designated the IRGC as a "foreign terrorist organization" in early April, an unprecedented move which further complicated the Middle East situation.