The United States acted Wednesday to financially clamp down on Syria's military intelligence chief, Assef Shawkat. The Treasury Department ordered US banks to block any assets found in the United States belonging to Shawkat. Americans also are barred from doing business with him. The department alleged that Shawkat has played a role in furthering Syria's "support for terrorism and interference in the sovereignty of Lebanon." It marked the United States' latest action to turn up the heat on Syria. In June, the department moved to block the assets of Syria's interior minister, Ghazi Kanaan, and its chief of military intelligence for Lebanon, Rustum Ghazali. The power for the department to take the action stems from a May, 11, 2004, executive order by President George W. Bush. Syria is on the State Department's list of countries and organizations accused of supporting terrorism. The United States continues to have diplomatic relations with Syria, but tensions have increased. Syria has come under intense international pressure since a truck bomb killed Lebanese leader Rafik Hariri in Beirut on Feb. 14. Syrian officials have been linked to the killings though they deny any involvement. The United States has demanded that Syria improve cooperation with a UN investigation of the assassination. Even Syria's exiled former vice president, Abdul-Halim Khaddam, recently fingered Assad as the responsible party in the Hariri killing. Syria has said that all of its military forces left Lebanon last April.