A slate of investigations into alleged terror plots and killings sponsored by Iran has opened a new front in U.S. efforts to persuade European governments to cut ties with Tehran following President Trump’s withdrawal from the nuclear deal in May.

Washington, Israel and Iranian dissident groups say the alleged recent operations show that Iran has ended years of caution about hunting its enemies in Europe. They are urging European governments to withdraw support for Iran and ban Iranian officials from the region.

But European officials, some skeptical that Iran’s government is behind the plots, are reluctant to adopt a harder line.

In late June, police in three European countries arrested an Iranian diplomat and three others in an alleged plot to bomb an Iranian opposition meeting outside Paris, marking a rare public confrontation between European security services and Iran.

In July, Dutch authorities said they had expelled two Iranian diplomats whom foreign officials say were linked to the assassinations of at least one Iranian dissident, Ahmad Mola Nissi. He was gunned down in November by a masked assassin in The Hague. U.S. officials believe Iran’s Ministry of Intelligence and Security was involved. Dutch authorities are investigating.