Donald Trump was forced to call for restraint on Sunday after Israel launched fresh airstrikes on Beirut as mediators sought to conclude negotiations on a preliminary peace deal between Iran and the US that would bring the three-month war in the Middle East to a definitive end.

Trump played down new Israeli strikes but said “all sides should stand down”.

“We are very close to a Deal that will bring peace to the region, including to Lebanon … There should be no more attacks by Israel anywhere in Lebanon, but there should also be no more attacks by any other party, including Hezbollah, against Israel. This could be the beginning of a long and beautiful peace – Let’s not blow it!” the US president posted to his social media site.

Trump had previously suggested the US could sign an agreement with Iran on Sunday, but as the evening came in the Middle East, there was no sign of a breakthrough. Instead, Iranian officials threatened a military response to the Israeli attack on Beirut, which destroyed a building in the Lebanese capital’s southern suburbs, killing three and injuring six.

Trump told the Axios news site that the Israeli strike had “delayed the signing by a few hours” and, using an expletive, said he had told the Israeli prime minister, Benjamin Netanyahu, he had no judgment.

Israel said it had targeted senior Hezbollah commanders after the militant Islamist organisation – which has close links with Tehran – launched three projectiles into northern Israel.

A strike on Beirut by Israeli forces a week ago triggered a short but intense new round of fighting between Iran and Israel, momentarily destabilising negotiations between Tehran and Washington.