The Biden administration is "very concerned" that the assassination of Hamas' political leader Ismail Haniyeh could derail ongoing negotiations over a ceasefire deal in Gaza, potentially increasing the risk of regional war, as reported by Axios on Wednesday, citing US officials.

According to the officials, this deal is central to President Biden's post-war strategy in the Middle East and is personally significant to him.

Haniyeh was the key negotiator with Qatari and Egyptian mediators. He was killed in Tehran as a result of an Israeli strike on his residence. Hamas and Iran condemned the aggression and vowed retaliation. US officials confirmed "Israel's" responsibility but stated the US was not involved.

Read more: Hezbollah announces martyrdom of Cmdr Fouad Shokor (Sayyed Mohsen)

The assassination has raised serious concerns among mediators, including Qatari Prime Minister Mohammed Bin Abdul Rahman al-Thani, about the future of the negotiations.

In a post on X, he wrote: "Political assassinations and continued targeting of civilians in Gaza while talks continue leads us to ask, how can mediation succeed when one party assassinates the negotiator on the other side? Peace needs serious partners and a global stance against the disregard for human life."

Despite this, US Secretary of State Antony Blinken "emphasized the importance of continuing to work to reach a ceasefire and hostage deal in Gaza," State Department spokesperson Matthew Miller said in a statement.

According to the sources, the Biden administration fears that Haniyeh's assassination, combined with a recent strike in a Beirut suburb by "Israel", could escalate tensions and potentially lead to a regional war.

Israeli officials, on their part, claimed they do not seek war and that the regime "remains prepared to respond to any attack by Hezbollah," a statement issued by the Israeli Security Ministry read. 

Read more: Iran, Russia call for urgent UN meeting on Hamas leader assassination

Earlier this morning, the IRGC announced the martyrdom of Ismail Haniyeh alongside one of his guards in Tehran.

Hamas later confirmed Haniyeh's martyrdom, noting that he was killed in a "treacherous Zionist airstrike on his residence in Tehran."

Iran's IRGC later said, "We are studying the dimensions of the martyrdom of Ismail Haniyeh, head of Hamas' political bureau, and will announce the results of the investigation later."

An op-ed published in the Financial Times earlier warned that the recent aggression against Lebanon and the assassination of Ismail Haniyeh could send the region into war.