Theresa May is increasing the number of British troops serving in Afghanistan to more than 1,000 for the first time in years as she heads to a crunch Nato summit where allies will come under intense pressure from Donald Trump to spend more on defence.

The prime minister committed an extra 440 troops to the international body’s capacity building mission in the country as she called on other European countries to match the UK’s 2% of GDP on defence spending.

Speaking ahead of the summit, the Nato general secretary, Jens Stoltenberg, said concerns about burden-sharing would be addressed. “Burden-sharing in Nato is not fair, that is why we have agreed to do something about it,” he told BBC Radio 4’s Today programme on Wednesday.

Ministry of Defence sources fear that the US president, who will attend the Brussels summit, could threaten to pull troops out of eastern Europe and refuse to contribute to joint Nato exercises unless they commit to boosting their contribution.

Before taking off on Air Force One, Trump tweeted about the US giving more money to Nato than any other country.

Donald J. Trump (@realDonaldTrump) Getting ready to leave for Europe. First meeting - NATO. The U.S. is spending many times more than any other country in order to protect them. Not fair to the U.S. taxpayer. On top of that we lose $151 Billion on Trade with the European Union. Charge us big Tariffs (& Barriers)!

In remarks which will alarm European defence chiefs, who are already anxious about his planned talks with Russian president Vladimir Putin next week, he added: “Nato countries must pay more, the United States must pay less.”

May, however, is expected to stress her commitment to Nato and underline the leading role the UK plays in the alliance, which defence sources fear could be under threat if Trump is persuaded to rethink his military commitments by Putin.

She will say: “Nato is as vital today as it ever has been and our commitment to it remains steadfast. The alliance can rely on the UK to lead by example, not just in meeting the 2% pledge but by contributing our cutting edge capabilities to operations around the world.



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“And we will continue to make the case for all allies to follow the UK’s example and meet the 2% pledge.”



The troop uplift to 1,100 will be the biggest UK military commitment to Afghanistan since David Cameron withdrew all combat troops four years ago after 13 years of fighting the Taliban.

A support mission of 450 stayed on to train domestic forces, which was later increased. It is this non-combat resolute support mission, backing up local forces in their ongoing fight against the Taliban, that will be boosted by the deployment.

The additional troops will initially deploy from the Welsh Guards, with around half of the 440 arriving in August and the remainder to follow by February 2019. It comes at a critical time ahead of national elections in October.

Britain is one of only five countries that currently meets the Nato targets of spending 2% of GDP on defence. Germany’s contribution is 1.2%, although Angela Merkel has said she knows that in needs to rise.

Defence secretary Gavin Williamson said: “Lasting peace and stability in Afghanistan will help keep the streets of Britain safe and this uplift signals our unwavering commitment to realising that future.”

Stoltenberg said there was a plan in place to address the concerns of the US. “European allies are stepping up after years of cutting defence spending,” he said. “Germany has to spend more on defence and Germany agrees, after two decades of reducing defence spending Germany has started to increase.

“Last year, it was 6% in real term... they have put forward plans to increase defence spending by 80% until 2024.”