The US ambassador to Belarus warned Thursday that Washington could impose new sanctions on the ex-Soviet nation over its refusal to free political prisoners and allow democratic freedoms. Ambassador Karen Stewart said the new measures, which would follow previous travel restrictions against Belarusian officials and sanctions against a state oil processing company, could target other state-owned Belarusian companies. "In the continued absence of progress on the part of the Belarusian authorities, the United States prepares to take further steps against other state enterprises," Stewart said at a briefing. She emphasized that the US administration considers six jailed Belarusian opposition activists to be political prisoners. Belarusian authorities have said the six, including Alexander Kozulin, a candidate in the 2006 presidential election, were serving their sentences for criminal offenses.