EU Deputy Secretary-General for Political Affairs Enrique Mora negotiated with officials in Tehran on Wednesday, while White House Coordinator for the Middle East and North Africa Brett McGurk held talks in Saudi Arabia, the report said.
The talks were aimed at persuading Tehran either not to respond to Israel or to take symbolic actions, the report read on Wednesday.
"Everyone since last night is putting pressure on Tehran to not respond and to contain this," one Western diplomat was quoted as saying by the newspaper.
On Wednesday, Hamas confirmed that Haniyeh was killed in an aistrike on his residence in Tehran after he took part in the inauguration of newly elected Iranian President Masoud Pezeshkian. The movement has blamed Israel and the United States for Haniyeh's death and said the attack would not go unanswered.