Nato leaders will gather in Lithuania this week where several topics about the future of the alliance will dominate the agenda.
The summit, which takes place on Tuesday and Wednesday in Vilnius, is the fourth to take place since the outbreak of the Ukraine war in February last year.
Much of the discussion will surround Sweden and Ukraine's Nato membership bids.
Defence spending and the decision to provide Ukraine with weapons, including controversial cluster bombs, will also be discussed.
Here are some key things to look out for at the two-day meeting:
Sweden and Ukraine membership
The summit looks set to be dominated by Ukraine's membership status.
President Volodymyr Zelenskyy has repeatedly insisted that Kyiv received an invitation, despite current rules barring such a move.
Nato Secretary General Jens Stoltenberg has made clear Kyiv will not become a member while the war with Russia continues.
Still, allies are divided over how swiftly Ukraine should be allowed to join after the fighting ends.
The US and Germany are wary of any move that might take the alliance closer to war with Russia, though other European nations are far more enthusiastic.
US President Joe Biden has described Kyiv’s bid as “premature”, telling CNN: “I don’t think its ready for membership in Nato.”
Britain on the other hand has indicated support for a fast-track approach for Ukraine.
Nato requires the unanimous approval of all 31 members to expand.
Sweden had hoped to become the 32nd member of the alliance but Turkey continues to block its accession, accusing Stockholm of harbouring members of militant groups on its territory and saying it must crack down on them before being allowed to join.
Allies hope Turkish President Recep Tayyip Erdogan will lift his opposition at the summit but it is unclear whether this will happen.
Hungary is also holding up approval of Sweden’s candidacy but has yet to make its reasons public. Nato officials expect Hungary will follow suit once Turkey lifts its objections.
Security assurances for Ukraine
In a bid to reassure Kyiv before it joins Nato, the US, Britain, Germany and France have been negotiating possible long-term commitments on weapons supplies.
Diplomats say these would fall outside Nato's framework and not commit the powers to sending troops to help Ukraine if it is attacked again.
Weapons supplies would build on the tens of billions of dollars' worth of arms Kyiv's backers have delivered since Russia invaded.
Drawing up an agreement similar to the US arrangement with Israel, under which Washington will send $3.8 billion of weapons each year for a decade, is one possibility.
Intelligence sharing, training and rebuilding Ukraine's own arms industry could also figure in a deal.
Diplomats say there would likely be an overall declaration of support after which individual countries would commit to bilateral assistance under that umbrella.
But Eastern European countries insist any agreements should not be a substitute for Ukraine's eventual Nato membership.
Bolstering Nato's eastern flank
The war in Ukraine has led to the biggest overhaul of Nato's eastern defences in a generation.
Leaders should sign off on new regional plans in Vilnius detailing how allies would stop any Russian attack at Nato's borders.
Diplomats say Turkey has thrown a spanner into the works with last-ditch objections but they expect Mr Erdogan to give his approval nonetheless.
The move is part of a package in which allies are boosting the number of high-readiness troops Nato can call on to 300,000.
Upgrading Nato's defence spending target
Nato allies have reached agreement to raise the alliance's target for military spending to at least 2 per cent of national GDP, according to two diplomats.
Mr Stoltenberg said good progress was being made.
“In 2023, there will be a real increase of 8.3 per cent across European allies and Canada. This is the biggest increase in decades,” he said, adding that European allies and Canada will have invested more than $450 billion extra since 2014.
Only 11 Nato countries are projected to hit the target this year despite public haranguing during the tenure of former US president Donald Trump.
The allies have now been negotiating a new pledge and have become more ambitious.
Nato through the years - in pictures
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British Foreign Secretary Ernest Bevin signs the North Atlantic Treaty in Washington on April 4, 1949. All photos: Getty -
The North Atlantic Treaty showing the signatures of the foreign secretaries and ambassadors of the original signing nations - Belgium, Britain, Canada, Denmark, France, Iceland, Italy, Luxembourg, the Netherlands, Norway, Portugal and the US -
A meeting of the North Atlantic Council deputies in 1951 in London, attended by Gen Dwight D Eisenhower, centre -
Lord Hastings Lionel Ismay, Secretary General of Nato, with the newly adopted Nato emblem in 1952 -
Belgian Foreign Minister Paul-Henri Spaak holds a press conference in Paris after taking over from Hastings Ismay as Nato chief in 1956 -
The opening speech at the Nato summit in Paris in 1957 -
Some of the Nato vessels gathered for Exercise Medflex Invicta in Malta in 1961 -
A McDonnell Douglas F-4 Phantom II fighter-bomber of the Royal Navy is launched from HMS Ark Royal during a Nato exercise in 1972 -
German Nato troops on manoeuvres in 1980 -
Lord Carrington, the new Secretary General of Nato, sits behind his desk in Brussels, Belgium, in 1984 -
A US Air Force F-15E Strike Eagle refuels in the skies over Macedonia in 1999, as it flies missions in support of Nato Operation Allied Force -
Frigates, part of the Nato permanent fleet based in the Mediterranean Sea, enter the port of Piraeus, Greece, in 2003 -
US President George W Bush, US Secretary of Defence Donald Rumsfeld, ambassador R Nicholas Burns and US Secretary of State Colin Powell attend the Nato summit in 2004 in Istanbul, Turkey -
Members of the military attend a commemoration for Nato soldiers during the 2009 summit in Kehl, Germany -
A protester throws a stone during clashes at the Nato summit in 2009 in Strasbourg, France -
A Polish soldier sits in a tank as a Nato flag flies behind during military exercises in Zagan, Poland, in 2015 -
Guests depart after attending the opening ceremony at the 2018 Nato summit in Brussels -
Nato leaders listen to British Prime Minister Boris Johnson while attending the summit in 2019 in Watford, England -
Soldiers from the Royal Welsh Battlegroup take part in manoeuvres during a Nato exercise on the Estonian-Latvian border in 2022 in Voru, Estonia -
Secretary General of Nato Jens Stoltenberg meets troops at the Tapa Army Base in 2022 in Tallinn, Estonia -
Polish soldiers hold a Nato flag in 2022 at a training ground in Orzysz, Poland -
Ukrainian President Volodymyr Zelenskyy and Mr Stoltenberg attend a joint press conference in Kyiv, Ukraine, in April 2023
Spending 2 per cent will become a minimum commitment despite opposition from countries such as Luxembourg and Canada.
But there are questions over how soon Nato will agree to hit that figure and whether it will seek to go further.
