The PM condemned the attack near the Syrian border which has sparked fears about escalating conflict across the region, as the UK blamed “Iran-aligned militia”.
“We are concerned and would urge Iran to continue to de-escalate tensions in the region,” Mr Sunak told broadcasters on a trip to the north-east on Monday.
The PM added: “We absolutely condemn what has happened over the past couple of days. My thoughts are with all of those impacted, those who lost their lives, their families and those that are injured.”
Mr Sunak said the UK would “resolutely with our allies to bring stability and peace to the region”, adding: “And that’s what we’ll continue to work towards.”
The Islamic Resistance in Iraq has claimed it is responsible for the strike. At least 34 US troops were also said to have been injured in the strike on the support base known as Tower 22 on Sunday.
US officials were working to identify the group behind the attack but have so far assessed that one of several Iranian-aligned groups was responsible. Mr Biden said in a written statement that the US “will hold all those responsible to account at a time and in a manner [of] our choosing”.
Iran has denied any involvement. Nasser Kanaani, spokesman for Iran’s foreign ministry, said it was “not involved in the decision making of resistance groups” in the way they choose to “defend Palestinians”. And Iran’s minister for intelligence Esmail Khatib said different groups make their own decision to attack “American aggressors”.
Foreign secretary Lord David Cameron said that Britain “strongly condemned” the attacks by “Iran-aligned militia groups” as he also urged Tehran to de-escalate the situation.
Labour leader Sir Keir Starmer has said those behind the deadly drone strike on a US base in Jordan should be “held to account” – but said everything must be done to prevent escalation. “I am concerned about the possibility of escalation of an already dangerous situation in the Middle East,” he told broadcasters.
“So we have to see this in that context and do everything that we can to ensure there isn’t escalation of the conflict, and on the contrary, that we find ways to bring this conflict to the immediate end.”
Asked whether MPs should get to vote on further UK military action, Sir Keir said: “I think it’s important that we judge each intervention on its merits.”
Since Hamas launched its attack on Israel on 7 October, Iranian-backed militias have struck American military installations in Iraq more than 60 times. In Syria, they have struck more than 90 times with drones, rockets, mortars and ballistic missiles.
Militias have said that their strikes are in retaliation for Washington’s support for Israel in the war in Gaza, and aim to push US forces out of the region.
The US in recent months has hit targets in Iraq, Syria and Yemen in response to attacks on its forces and to diminish the threats from Iranian-backed Houthi rebels to commercial shipping in the Red Sea.
Britain has joined two strikes against the militants in Yemen, though they so far seem to have done little to deter Houthi action. A British-linked oil tanker went up in flames after a strike claimed by the Yemen-based group on Friday before a further attack on HMS Diamond was successfully repelled.
Meanwhile, No 10 also defended the pause in funding for UNRWA over allegations staff from the agency helped Hamas with its 7 October attack on Israel.
Downing Street said no further funding had been expected to be released to the agency in the coming weeks.
Mr Sunak’s spokesperson said: “My understanding is that we have committed £16 million to UNRWA following the Hamas terror attacks, but this was dispersed before the allegations came to light.”
Labour’s Jonathan Ashworth said the allegations “absolutely appalling” – but argued the UN agency’s programmes should be allowed to continue.
The shadow cabinet minister told Sky News: “What is happening is a catastrophe which is why, for example, we’ve also called for a halt in the fighting, an immediate humanitarian truce, a ceasefire, a sustained ceasefire is needed, but UNRWA programs have to continue.”