US President Joe Biden on Thursday said that the killing of Hamas leader Ismail Haniyeh was not helpful for the ceasefire talks in Israel's war on Gaza.

Following Haniyeh's assassination in Iran, tensions in the middle-east have been on the rise, with Iran's supreme leader also taking a vow of "revenge".

Hamas and Iran's Revolutionary Guards had confirmed the death of Haniyeh, who had participated in the internationally-mediated indirect talks on reaching a ceasefire in Gaza.

Haniyeh had attended the swearing-in ceremony of Iran's new president Masoud Pezeshkian, hours after which, a strike hit the Hamas leader's Tehran residence, leaving him dead.

When asked if Haniyeh's assassination ruined the ceasefire agreement possibilities, Biden said, "It doesn't help." The US President said that he also had a conversation with Israeli Prime Minister Benjamin Netanyahu on Thursday, Reuters reported.

Netanyahu's administration though has not claimed responsibility for the assassination, it has said that the nation had delivered heavy blow to Iran's proxies including Hamas and Lebanon-based militant group Hezbollah in the recent times.

Israel has made it clear that it would respond to any attack with full force.

Concerns of an all-out conflict breaking out between Israel and Iran have been widening in the region, which is already on the edge amid the war on Gaza, where tens of thousands of Palestinians have lost their lives.

Last week, Netanyahu had addressed Congress in Washington as he sought to bolster the United States' support for his country's fight against Hamas and other Iran-backed groups.

He signalled that a ceasefire deal could be taking shape after nine months of war, but during his speech to the Congress, he vowed to press forward with Israel's war until he achieves "total victory".

Conflict in the region sparked when Hamas launched an unprecedented attack on Israel on October 7, killing 1,200 people and talking around 250 hostages.

Meanwhile, Gaza's health ministry had said that since Israel's offensive began on the region, nearly 40,000 Palestinians have been killed and almost the entire population of 2.3 million have been displaced.