WASHINGTON — The Trump administration on Thursday piled new economic sanctions onto its ever-growing pressure campaign against Iran, but it also opened access to medicine for cancer and organ transplant patients in an effort to turn Iranians against their leaders.

The medicines are being sent to Iran through businesses in Switzerland, whose government has acted as a conduit between Washington and Tehran. Brian H. Hook, the State Department’s special envoy for Iran policy, said at least one European company had already delivered the prescriptions to patients.

Mr. Hook accused Iran’s clerical government of diverting millions of dollars for medical supplies to buy items like electrical cable and tobacco products. In other cases, he said, Tehran sold medicines on the black market and used the profits to fund its military proxies in Yemen, Syria, Lebanon and Iraq.

“I’m sure there are more examples we don’t know about, but the Iranian people know that their regime, not American sanctions, are to blame for their difficulties getting medical supplies,” Mr. Hook told reporters.