The U.S. Treasury Department has barred Americans from doing business with three subsidiaries of the Belarusian state-run oil company Belneftekhim as part of sanctions against Belarus.

Thursday's action expands measures taken against Belneftekhim in November after U.S. authorities determined that the firm had helped support Belarusian President Alexander Lukashenko's repressive moves against political opponents. The order specifically bars contact with the firms Lakokraska OAO, Polotsk Steklovolokno OAO and the Belarusian Oil Trade House in efforts to prevent Belneftekhim from using other firms and subsidiaries to get around the U.S. measures.

The sanctions stem from a 2006 executive order from President Bush aimed at isolating President Lukashenko because of his poor record on human rights and civil liberties.

The United States and the European Union accuse him of jailing opponents, restricting news media freedom and rigging elections.