President Barack Obama hit back at the health insurance industry on Thursday, accusing it of attempting to mislead Americans about healthcare reform and promising to overhaul the industry in Congress.

Obama criticized insurance firms for running marketing campaigns in spite of Democrats’ attempts to reform the health system.

Obama said a decrease in health insurance companies’ stocks this week increased the industry’s nervousness that a healthcare reform law might pass.

Obama has made his move for a healthcare reform bill that expands insurance coverage and cuts fees which is his leading domestic priority. He received a boost this week when a Senate Finance board approved its version of a reform measure with the support of Republican Senator Olympia Snowe.

Health insurer stocks were trading lower on Thursday afternoon. The Morgan Stanley Healthcare Payor index fell 1.8% while the broader S&P 500 index was higher.

Shares of Cigna had been off 2.6 percent, Humana fell 2.2 percent, while WellPoint fell 1.6 percent.