Britain is set to provide Saudi Arabia with limited defensive military support after the kingdom requested assistance to counter attacks by Yemen's Iran-backed Houthi rebels, with an RAF Voyager aircraft expected to begin operations within days.
The support will involve air-to-air refuelling and is expected to be carried out by a single Voyager aircraft operating from RAF Akrotiri in Cyprus. UK officials said the deployment will be time limited and is initially expected to run for several weeks.
The prime minister approved the request after receiving advice from Defence Secretary Wes Streeting and Foreign Secretary Ed Miliband.
British officials said the defensive role could include supporting Saudi fighter jets as they respond to incoming Houthi drones and ballistic missiles.
The move comes as Saudi Arabia faces renewed attacks from the Houthis, who have in recent days claimed responsibility for drone and missile strikes targeting the capital Riyadh and energy facilities along the Red Sea coast.
The Houthis are fighting Yemen's internationally recognised government, which receives backing from Saudi Arabia.
Britain's contribution is expected to be relatively limited, with only one Voyager aircraft involved. The aircraft is part of the RAF's core fleet of nine Voyagers, eight of which are military registered while another is civilian registered. The RAF also has five additional aircraft that can be recalled for military use if required.
Speaking to reporters travelling with him to the United Nations General Assembly in New York, Burnham said the decision was linked to protecting Britain's interests and limiting the effect of further disruption on the region and the cost of living.
"I go back to the point I made about cost-of-living pressures and acting to secure the interests of Britain and the wider region," he said.
"Because of course Saudi Arabia has been experiencing attacks, is looking at potential further disruption, and we need to keep those pathways open, and hence our agreement to the request."
The Red Sea is an important route for international shipping, making continued disruption in the region a concern for Saudi Arabia and other countries that rely on the waterway.
The Houthis recently took control of the strategic port city of Mokha and Perim Island, which sits at a key gateway to the Red Sea. The area is part of an important shipping route used by Saudi Arabia.
Britain's decision to send one refuelling aircraft represents a limited form of military assistance compared with direct combat operations. UK officials have stressed that the deployment will be temporary, with the initial commitment expected to last only a few weeks.
The latest escalation comes against the backdrop of a conflict in Yemen that has continued, on and off, since 2014. The situation has also become more complex because of the Houthis' links to Iran, which is involved in its own tensions and conflict with the United States.
The British government has also indicated that its existing defence relationship with Saudi Arabia includes air defence support.
Energy Minister Martin McCluskey told MPs last week that the UK was "providing air defence support" to Saudi Arabia through the two countries' defence partnership, although he did not give details about operational military activity.
There are also signs that other European countries could become involved in supporting Saudi Arabia.
Nato Secretary-General Mark Rutte said in a BBC interview last week that European allies could be discussing how to respond to the situation.
"I would not be surprised if some phone calls were taking place between European allies, 'hey, how are we going to deal with this?'.
"Let's see what happens, and if Nato can help, we will always be helpful."
Britain has previously taken direct military action against the Houthis.
In January 2024, the UK joined the US in carrying out air strikes against Houthi targets in Yemen after attacks on shipping in the Red Sea, including an incident involving a Royal Navy warship.
Then-Prime Minister Rishi Sunak said the UK had "acted in self-defence" and described the strikes as "necessary, proportionate, and targeted" to protect lives and commercial shipping.
Further joint air strikes by Britain and the US followed later in 2024.
The latest UK deployment is therefore a more limited form of involvement, focused on defensive support for Saudi Arabia as the country responds to continuing Houthi missile and drone attacks.