World Bulletin / News Desk

Trump has repeatedly berated European NATO members and Canada for lagging on a pledge to aim to spend two percent of GDP on defense, and he harangued them again on Twitter on Monday.

- How much does the US spend on NATO? -

Trump claimed on Monday that the United States was "paying for 90 percent of NATO", though it is not clear how he arrived at this figure.

According to alliance figures, the US will account for just under 70 percent of defense spending in NATO in 2018 -- $706 billion out of the just over $1 trillion spent by all 29 members this year.

In raw terms, Britain is the next biggest defense spender with an estimated $62 billion in 2018, followed by France with $52 billion and Germany with $51 billion.

- The 'two percent' pledge -

Raw expenditure figures, however, do not take into account the relative size of each country's economy, and NATO countries have made defense spending commitments based on their gross domestic product.

In 2006 NATO defense ministers agreed as a guideline that they should spend at least two percent of their GDP on defense. But as the financial crisis hit, many cut military budgets.

At the Wales summit in 2014, alarmed by declining military spending across the alliance and as the Ukraine crisis raged, NATO members pledged to "aim to move towards the two percent guideline within a decade".

Trump has repeatedly used this pledge to say that NATO countries which are not already hitting the two percent target are breaking a promise, but diplomats point out that this is not strictly speaking what was agreed -- though almost all agree they need to spend more.

If all NATO allies did hit the two percent target it would translate into an extra $110 billion spent on defense.

- Who's hitting the two percent target? -

The US is by far NATO's biggest spender in terms of GDP as well as raw expenditure, shelling out an estimated 3.5 percent of GDP on defense in 2018, according to NATO figures.

Greece is second, with 2.27 percent followed by Estonia with 2.14 percent and Britain with 2.1 percent. Latvia comes in at exactly two percent, while Poland, Lithuania and Romania are all expected to clear the threshold later this year.

Germany, Europe's economic powerhouse, lags on 1.24 percent and has come in for withering criticism from Trump, though his defense chief Jim Mattis last month praised Berlin's efforts to step up spending on its creaking armed forces.

The sheer size of Germany's economy makes it difficult for Chancellor Angela Merkel to quickly boost the percentage of GDP spent on defense.

- Defense spending vs spending on NATO -

At times Trump has suggested NATO allies "owe" money to the alliance. This slightly confuses the two percent pledge, which relates to spending on their own defense budgets, with financial contributions made directly to NATO.

Direct contributions to NATO are used to pay the organization's so-called "civil budget" -- 248 million euros in 2018 which finances NATO's command structure.

All 29 members contribute according to an agreed cost-sharing formula based again on the size of their economies. As the biggest economy, the US pays 22 percent of the total, followed by Germany with 14 percent and France and Britain with 10.5 percent.