The US special envoy for Iran told a congressional hearing that Tehran was “without question” behind last week’s attacks on two tankers in the Gulf of Oman.

“Those who have seen the intelligence all come away without any question Iran is behind these attacks,” Brian Hook told the House Committee on Foreign Affairs.

The United States sought on Wednesday to bolster its case for isolating Iran over its nuclear and regional activities by displaying limpet mine fragments it said came from a damaged oil tanker and saying the ordinance looked Iranian in origin.

Both Trump and Iran said they are not seeking war, but many lawmakers fear that as the US builds up its forces in the region, it increases the chances of the two sides being accidentally drawn into a conflict.

“No one should be uncertain about our desire for peace or our readiness to normalize relations should we reach a comprehensive deal,” Hook said. “We have put the possibility of a much brighter future on the table for the Iranian people.”

Hook told lawmakers that Iran has chosen to use military force despite Trump’s Iran policy largely relying on diplomatic and economic tools like sanctions.

“Our policy is at its core an economic and diplomatic one. Recently, however, Iran has responded to it with violence. Iran should meet diplomacy with diplomacy, not with terror, bloodshed and extortion” he said.

On Monday, Iran said it could soon start enriching uranium to just a step away from weapons-grade levels, breaching a cap that was set under the nuclear deal abandoned by the United States. The announcement followed warnings from President Hassan Rouhani that a new deal needs to be in place by July 7 or the Islamic Republic would increase its enrichment of uranium.