"Israel's" assassination of the head of Hamas' political bureau Ismail Haniyeh was not helpful for efforts aiming at reaching a ceasefire in Gaza and a prisoner exchange deal between the Palestinian group and Tel Aviv, US President Joe Biden acknowledged on Thursday.

"It has not helped," Biden said when asked if Haniyeh's assassination in Tehran ruined ceasefire talks.

He made the comments at Joint Base Andrews, Maryland, where a plane carrying American detainees released by Russia landed as part of a prisoner swap.

Although Netanyahu's government has not commented on the assassination of the Hamas leader, the Palestinian Resistance group has blamed "Israel" for the attack.

The US president confirmed that he held a "very direct" talk with Israeli occupation Prime Minister Benjamin Netanyahu earlier on Thursday and urged him to leverage the opportunity to reach a ceasefire deal swiftly.

Biden also indicated he was "very concerned" about the soaring tensions in the Middle East.

The White House said that Biden assured Netanyahu during a call following Haniyeh's assassination on Thursday of Washington's unwavering commitment to defending "Israel's" security "against all threats from Iran."

During the call, which included Vice President and Democratic presidential candidate Kamala Harris, Biden also highlighted "ongoing efforts to de-escalate broader tensions in the region," according to a White House statement.

The call took place shortly after "Israel" declared it had assassinated Hezbollah's top military leader Sayyed Fouad Shokor in Beirut.

In a readout of the call, the White House mentioned that Biden "reaffirmed his commitment to Israel's security against all threats from Iran," including what he described as Tehran's proxy groups Hamas, Hezbollah, and the Yemeni Ansar Allah movement.

The US president also discussed "efforts to support Israel's defense against threats, including ballistic missiles and drones, to include new defensive US military deployments," the statement said.

"Israel" has indicated that Shokor's assassination was in response to a deadly rocket fire it blamed on Hezbollah targeting the occupied Syrian Golan Heights last week, a claim that the Lebanese Resistance group categorically denied.

Read more: WH 'very concerned' over ceasefire talks after Haniyeh's assassination