Nato leaders including President Trump and Prime Minister Keir Starmer are meeting to agree a big increase in defence spending, but nearly a third of the alliance's members have not reached the existing spending target.
The new target will be to spend 5% of the size of their economies, measured by GDP, on "core defence" along with defence-related areas such as security.
But the latest Nato estimates show nine members spent less than the existing target of 2% of GDP.
Trump has been critical of the lowest spender, Spain which he called "notorious" for its "low spending".
Rachel Ellehuus, director of the defence think tank Rusi sees evidence of a spending split within Nato, along geographical lines.
