Pompeo, who has been attending a North Atlantic Treaty Organisation summit in Brussels flew in from Abu Dhabi, where he discussed Iran with leaders of the United Arab Emirates.
The secretary of State's comments came as the US steps up pressure on Iran after President TrumpDonald John TrumpMcConnell to meet with Trump's Supreme Court pick Tuesday Kavanaugh offers lengthy judicial record ahead of bitter confirmation fight Hundreds protest Kavanaugh's nomination outside Supreme Court MORE's announcement in May that he would withdraw from the 2015 nuclear deal with Tehran, which sought to curb Iran's nuclear ambitions in exchange for sanctions relief. However, Iran was now "treating us with much more respect right now, than they did in the past", Trump added.
In another post, he said "Iran continues to send weapons across the Middle East, in blatant violation of UN Security Council resolutions".
"Iran's regime wants to start trouble wherever it can. It's our responsibility to stop it".
Referring to earlier reports that Iran could do away with special privileges if India cut its oil imports, former ambassador to Saudi Arabia, Oman and the UAE, Talmiz Ahmad, said this appeared to be "posturing".
"Just this past week there were Iranians arrested in Europe who were preparing to conduct a terror plot in Paris, France".
Speaking to Sky News Arabia, Pompeo said on Tuesday that a focus remains on denying "Iran the financial capacity to continue this bad behaviour".
This follows last week's failed Iranian-led terrorist attack in France, which was meant to target an Iranian opposition group.
Assadi was detained earlier this month near the German city of Aschaffenburg on a European warrant after the couple with Iranian roots was stopped in Belgium and authorities reported finding powerful explosives in their vehicle.
An Iranian diplomat was remanded in custody in Germany on Wednesday on charges of acting as a foreign agent and conspiracy to murder.
Assadi was believed to be a member of Iran's Ministry of Intelligence and Security, which is tasked with the "observation and fight against opposition groups inside and outside Iran", the prosecutors' statement said.
Prosecutors have said that, in March, Assadi ordered a married couple living in Antwerp "to carry out an explosives attack" on the rally and had handed them the explosives in a June meeting in Luxembourg.
Belgian authorities are also seeking Assadi's extradition over the alleged plot.
They had allegedly planned to bomb the rally by an exiled Iranian opposition group in Villepinte near Paris that was attended by several United States politicians.