Donald Trump said an Israeli strike on Beirut "should not have happened" after it triggered a strong protest from Iran, casting doubt on the US president's pledge that a peace deal would be signed Sunday.The attack does not appear to have entirely dashed hopes for an accord, however, with both sides signalling channels of dialogue were still open, and Trump maintaining a deal was still "close".Tehran has repeatedly insisted that any agreement to halt the war must include the parallel conflict in Lebanon, where Israel has been pursuing a campaign against the Iran-backed movement Hezbollah.But after days of momentum building towards a deal, Sunday's strike in Beirut's southern suburbs -- a Hezbollah stronghold -- prompted Iran's chief negotiator to question the point of continuing peace talks.The attack "showed that the United States either lacks the will to implement its commitments or lacks the ability to do so", Iranian parliament speaker Mohammad Bagher Ghalibaf said on X."If you do not have the will or the ability to fulfil your commitments, then there is no point in talking about continuing down this path," he added.Trump -- who over weeks of negotiations has repeatedly declared an accord with Iran was all but concluded -- said after the attack that a deal was still at hand, urging those involved not to "blow it"."We are very close to a Deal that will bring peace to the region, including to Lebanon, and all sides should stand down," Trump said on social media."This morning's attack on Beirut should not have happened, particularly on a special day," he added, possibly a reference to his hopes of a signing on Sunday, his 80th birthday.