Sir Keir Starmer defended plans to join the EU’s loan for Ukraine, claiming "it outweighs the cost".
The Prime Minister argued the continent must "move at pace" to boost defence.
The comments come after attending the European Political Community summit in Armenia.
Sir Keir Starmer has spoken of heightened "tension" between Donald Trump and Europe at a gathering of leaders from across the continent
Sir Keir has also spoken of heightened "tension" between Donald Trump and Europe during the gathering.
President Trump withdrew 5,000 troops from Germany due to European allies' refusal to pitch in with offensive action against Iran.
Speaking in the plenary session, Sir Keir said: "We cannot deny that some of the alliances that we have come to rely on are not in the place we would want them to be.
"There is more tension in the alliances than there should be and it’s very important that we therefore face up to this as a group of countries together."
Sir Keir Starmer said the benefit of joining the EU’s loan for Ukraine 'outweighs the cost'
|GETTY
The Prime Minister also said the damage done to economies around the world by the Middle East crisis would "play out with our electorates in all of our countries".
Sir Keir announced that Britain would start talks to access the European Union’s £78billion loan for Kyiv.
In a readout of a meeting on Ukraine he co-chaired with France in the margins of the summit, a Downing Street spokeswoman said: "The leaders discussed the European Union’s £78billion loan to Ukraine, and the Prime Minister underlined the opportunity the UK’s involvement would bring for both Ukraine and European security."
Other attendees included leaders from Ukraine, France, Italy, Poland, Norway, Finland, Nato, the European Commission and the European Council – as well as Canada, the first non-European nation to participate in the European Political Community (EPC).
LATEST DEVELOPMENTS:
The Prime Minister argued the continent must 'move at pace' to boost defence
|GB NEWS
The loan initiative was recently approved by the EU after Viktor Orban’s defeat in Hungarian elections, ending a long-running impasse.
Sir Keir said the UK’s involvement in the initiative would be "very good" for Ukraine’s military capability, for British jobs and for UK-EU relations.
The UK and EU, which will hold another joint summit this summer, will negotiate the parameters of access to the loan in the coming weeks, No 10 said.
The Prime Minister has been told by Brussels to pay up to £1billion a year by the EU in order to gain further access to the treaty's single market.
Sir Keir Starmer is currently in Armenia and has started talks to join the EU's loan to Ukraine
| GETTYSpeaking to GB News, Reform UK's Home Affairs spokesman, Zia Yusuf, accused the Prime Minister of using "any excuse" to cosy up to the Union.
He fumed: "Since the British public voted famously for Brexit, the political establishment, including Keir Starmer, have done a great deal to try to undermine that vote.
"MPs have basically decided that the public were wrong and they were going to look to find any excuse to try and get Britain back into the European Union by the front door or by the back door."
He added: "The billion-pound cost pales into insignificance. I think it's going to be much, much higher than that in raw absolute terms. And it looks increasingly like Keir Starmer now, he's always in a place where he's got nothing to lose."