Brian Hook, the U.S. envoy for Iran, insisted today that the Trump administration’s "maximum pressure" campaign is working, despite escalating tensions and growing fears of war.

Between the lines: Asked to justify that claim of success, Hook told members of a House Foreign Affairs subcommittee that funding to Iranian proxies had dropped, and argued with limited evidence that the regime is now "weaker." He didn’t deny that withdrawing from the 2015 nuclear deal and ramping up sanctions had rendered Iran more aggressive, rather than less.

On the nuclear deal...

Hook claimed that the Iran deal made Iran "stronger" and would have led to an "inevitable" showdown as its provisions began to lapse.

“Rather than wait for all of these things to come to pass in 10 years when Iran is stronger, we have pulled that forward. But I truly believe everything we are seeing today is inevitable.”

The backdrop: The European signatories are working desperately to save the deal, which Hook acknowledged Iran had complied with. Tehran has said it will breach the deal’s limits on enriched uranium in about a week.

On potential military action...

Hook refused to rule out a justification for military action against Iran based on the 2001 Authorization for the Use of Military Force (AUMF), which Congress passed in response to the September 11 attacks.

The backdrop: There is bipartisan concern about such a scenario on Capitol Hill. The New York Times reported Wednesday that Secretary of State Mike Pompeo and Pentagon officials have told Congress that they see a pattern of ties between Iran and Al Qaeda, which some lawmakers view as a dubious claim that could be used to invoke the AUMF.

On recent attacks…

Hook said that after seeing U.S. intelligence on the recent tanker attacks near the Strait of Hormuz, "all come away without any question that Iran is behind these attacks."

The backdrop: Allies including Germany and Japan had sought more information from the U.S. before assigning blame, but German Chancellor Angela Merkel said Tuesday that the evidence against Iran was "strong."

On Trump's views...

Hook said President Trump's description of the tanker attacks as "very minor," in an interview with TIME, was made in light of the fact that "very significant" attacks against U.S. interests had been anticipated.