Pompeo scrapped a day of mostly ceremonial events in Moscow on Monday in favor of the Brussels stopover.
What is the Iran nuclear deal?
President Hassan Rouhani issued an ultimatum to the Europeans, threatening that Iran would go further if they fail to deliver sanctions relief to counterbalance US President Donald Trump's renewed assault on the Iranian economy within 60 days.
Washington has warned shipping companies that "Iran or its proxies" could be targeting maritime traffic in the Persian Gulf region and said it was deploying an aircraft carrier and B-52 bombers to the Persian Gulf to counter alleged threats from Tehran.
This is coming on the heels of Tehran's plans last week to partially withdraw from a 2015 deal with major powers.
Hunt, who was due later to meet Pompeo along with the foreign ministers of France and Germany and the EU's diplomatic chief, also expressed concern about the risks of a nuclear arms race in the Middle East if Iran were to acquire such weapons. "He's always welcome obviously, but there are no precise plans at the moment", Mogherini said.
The EU is trying to implement a new channel to allow Iran to sell its oil and circumvent newly-instated USA sanctions, but setting it up is proving complex.
"This is already the most unstable region in the world and this would be a massive step in the wrong direction", he added. In September past year, he said he was "disturbed and indeed deeply disappointed" by the EU's decision to bypass United States sanctions.
The official said one primary focus of the meeting would be Trump's desire to modernize and expand existing arms control agreements, particularly ahead of the formal US withdrawal from the Intermediate Nuclear Forces treaty in August after Washington's repeated complaints that Moscow was violating it. Trump has said he wants new arms control accords that reflect the current post-Cold War situation and bring in other nations, notably China.
Russia's alleged meddling in U.S. affairs, including in the 2016 presidential election that resulted in Trump's victory, has never been proven. The Russian Foreign Ministry announced yesterday that Wang Yi is to visit May 12-13, and meet Russian Foreign Minister Sergey Lavrov on May 13 in Sochi.