Live Updates: NATO Leaders Summit on Bloc's 70th Anniversary: Day One

"We're here because NATO is an aggressive military alliance. Donald Trump is a racist and misogynist and someone fundamentally opposed to the rights of working people. And our message to the government is that we shouldn't be wasting our money in support of an alliance responsible for some of the worst foreign policy blunders of the last 20 years," John Reese of Stop the War / Don't Extradite Assange Campaign said. 

US President Donald Trump told reporters in London on Tuesday that next year's G7 Summit will be held at Camp David in Maryland.

"We're going to do it at Camp David," Trump said when asked whether he had picked a new site for the G7 summit.

Trump added they will be doing some "special things" at Camp David and mentioned it was a site many people liked.

In October, the White House faced a lot of backlash when it announced the controversial decision to use the Trump National Doral Miami resort venue to host the G7 summit on 10-12 June.

Trump still has not ruled out inviting Putin to next year's G7 summit.

"With all the differences between members, and we need to address them, we need to talk about the future of NATO and our common strategic interests, I'm going into this meeting relatively optimistically," Merkel said.

The United States will deal with those nations that do not spend enough on NATO from the standpoint of trade, US President Donald Trump said on Tuesday.

"Some countries that aren't fulfilling their commitments, those countries are going to be dealt with, maybe I’ll deal with them from a trade standpoint, maybe I’ll deal with them in a different way," Trump said.

On Friday, NATO Secretary-General Jens Stoltenberg said plans for member states to increase defence budgets by a combined $400 billion by 2024 marks "unprecedented progress" but allies must not become complacent.

According to NATO figures, the majority of states will meet guidelines stipulating that countries must allocate 2 per cent of their GDP to defence spending. In 2019, nine allies will meet this target, Stoltenberg announced.

The latest figures will seek to cool tensions within the alliance arising from US President Donald Trump’s criticisms of NATO allies for failing to meet defence spending targets. The US currently allocates the highest proportion of its GDP to defence spending and Trump has threatened to withdraw from the alliance if other states do not follow.

"Russians want a treaty and so do we - it could be a great thing," US President Donald Trump told journalists in London.  

"I will not promise that, but what I can say is that we are working on that. But it is not like NATO doesn't have a plan to defend the Baltic countries," Stoltenberg  said.