The U.S. will sanction nine petrochemical companies from Belarus next month unless President Alexander Lukashenko releases political prisoners and starts talks with his opponents, the State Department said Wednesday.

“Regrettably, we find the human rights situation has deteriorated to arguably the worst point in Belarus’s independent history,” spokesman Ned Price said during a press briefing.

State-owned petrochemical giant Belneftekhim, the Naftan refinery and seven other companies may lose protection under a general license from the Treasury Department that was issued in 2015 after Lukashenko released a previous batch of political prisoners.

With more than 300 political activists in prisons again, the State Department is unable to recommend the annual extension of the license, Price said. The step is “reversible” if Lukashenko releases his jailed opponents, stops violence and starts negotiations with the opposition under auspices of the Organization for Security and Cooperation in Europe.

Lukashenko, in power since 1994, secured his sixth term in office last year, triggering an unprecedented wave of popular protests. The U.S. and European Union haven’t recognized results of the election. The country’s exiled opposition leader Sviatlana Tsikhanouskaya hopes to start negotiations with Lukashenko or people in his circle around May and hold new, free and fair elections under international observation this fall. So far, Lukashenko has given no public sign of being willing for such talks.