Washington: The US official working to save the Iran nuclear deal said Wednesday that he held “very constructive” talks with key European allies, but could not say whether it would satisfy President Trump, the chief critic of the disarmament accord.

Brian Hook, the State Department director for policy planning, said a round of talks in Vienna last week with diplomats from Germany, France, Britain and other signatories to the 2015 accord were aimed at fixing what Trump sees as major flaws.

The talks left several issues unresolved, Hook told reporters on a conference call.

Trump has threatened to withdraw in mid-May from the accord, which forced Iran to dismantle much of its nuclear infrastructure, unless European cosignatories revise so-called sunset clauses that allow some restrictions to expire over time.

Trump also wants the Europeans to agree to more intrusive inspections in Iran and find ways to punish the Islamic Republic for its ballistic missile programme.

“Where we have agreement, we are capturing the agreement, and where we have differences, we are working to narrow them to see if we can reach an agreement,” Hook said.

The Europeans prefer to address any flaws in the deal with supplemental measures and not begin to chip away at the existing agreement, known formally as the Joint Comprehensive Plan of Action.

Doing the latter, they argue, could cause the delicate diplomatic balance that negotiated the accord to fall apart and give Iran a pretext to revive its nuclear programme.

Tehran has said it would reject any attempts to renegotiate the deal.

Hook conceded that Iran was in “technical compliance” with its nuclear obligations but continued a pattern of “aggressively destabilising” the region through support for armed groups in Iraq, Yemen, Lebanon and elsewhere, issues not covered in the agreement.

He said he was also working on “contingency plans” if the talks fell apart.

Iran was freed from international economic sanctions as long as it complied with the deal.

Trump is threatening to reinstate US sanctions unilaterally if his concerns are not met.