The resumption of U.S. strikes against Iran has thrust incoming UK prime minister Andy Burnham into a potential day one decision on how much to support Britain’s closest ally in its controversial military campaign.

Even as Burnham was installed as leader of the governing Labour Party on Friday, outgoing Prime Minister Keir Starmer’s government was engaged in high-level talks about renewed U.S. attacks on Iran, according to people familiar with the matter. The premier-in-waiting was kept appraised of the strikes, which entered their seventh consecutive night, said the people who asked not to be named while discussing sensitive security issues.

The strikes represent an early test for the former Greater Manchester mayor, as U.S. President Donald Trump threatens to target Iran’s civilian infrastructure in ways that could be seen as violating international law. While Starmer refused to join in on the initial sorties in February, he has subsequently allowed British bases to be used for so-called defensive strikes aimed at degrading Iran’s military capabilities and countering its threat to the Strait of Hormuz.

The U.S. has relied on British military facilities, such as RAF Fairford in Gloucestershire, as a launching-off point for such missions into the Middle East. Trump has nonetheless railed against Starmer, accusing Britain of failing to come to the U.S.’s aid in a time of need.

The new wave of strikes by the U.S. and the risk of an escalating conflict have led to renewed discussions in the British government in recent days, including on Friday, about whether to continue to approve the use of the bases. British officials are particularly concerned about Trump’s threats to bomb Iranian civilian infrastructure.

Burnham has been kept informed of the situation and his team has been in contact with government officials managing the response to the conflict, according to people familiar with the matter. Spokespeople for No. 10 Downing St. and Burnham’s office declined to comment.

Burnham has said little about his foreign policy during the weeks that he’s been the odds-on favorite to succeed the unpopular Starmer. During an earlier stint in Parliament, he voted in support of the Iraq War, but against the expansion of military action against Islamic State in Syria.

The incoming prime minister said earlier this week that he planned be “upfront” with Trump and “meet him where he’s at” when the two finally meet. “It’s about respecting the office, the relationship — the UK-U.S. relationship — but where you disagree, do it, but do it in a way that is kind of meeting him where he’s at,” Burnham said on the Goalhanger podcast.

UK officials are preparing to tell Burnham after he becomes prime minister that they believe Trump is serious about his threats to bomb Iranian civilian infrastructure if Tehran does not come to the negotiating table, Bloomberg reported on Friday.

The briefing will also say the U.S. calculates Trump’s blockade of the Strait of Hormuz is effective leverage against Iran so long as it remains in place for a lengthy period, potentially pointing to a drawn-out next phase of the conflict, according to the people.

Government officials are privately warning that Burnham may be immediately required to work with international leaders to try to deescalate the situation in the Middle East. That would take his focus away from the domestic policy agenda he had intended to push during his first few days in power, including announcements including on fossil fuel drilling in the North Sea and public control of the water industry.

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