British Prime Minister Keir Starmer insisted he was not "reversing Brexit" as he set out plans for a new treaty with Germany as part of a wider "reset" of relations with the European Union.
Starmer, who agreed that a deal with Germany would be in place by the end of the year following talks with counterpart Olaf Scholz, said it was a "once-in-a-generation" opportunity.
Scholz said the UK and Germany were "good friends, close partners and trusted allies" as Starmer promised a "bright new future" for the countries' relationship.
Starmer said the new UK-Germany treaty would result in "deeper links on science, technology, development, people, business, culture" and "a boost" to bilateral trading relations.
A new defence agreement will build on the "already formidable" co-operation between the two countries, Starmer said.
He said the treaty was a "once-in-a-generation chance to deliver for working people in Britain and in Germany."
"Britain can advance its interests much more effectively when we work with friends and partners.
"This treaty is part of a wider reset, grounded in a new spirit of cooperation with our shared understanding that this will be developed at pace, and that we hope to have agreed it by the end of the year."
The two countries also agreed to develop a "joint action plan to tackle illegal migration."
Starmer's hopes for the "wider reset" with the European Union would not amount to undoing the Brexit decision, he insisted.
"I'm absolutely clear that we do want a reset.
"I have been able to repeat that here today, a reset with Europe, a reset with the EU.
"That does not mean reversing Brexit or re-entering the single market or the customs union, but it does mean a closer relationship on a number of fronts, including the economy, including defence, including exchanges, but we do not have plans for a youth mobility scheme."
An agreement on youth mobility has been suggested by Brussels and could be a key demand in any negotiations.
But that could be seen as a step towards the restoration of free movement and Starmer said he had "clear red lines" ahead of talks with the European Union on the future relationship.
He told reporters: "In relation to youth mobility, obviously, we've been really clear – no single market, no customs union, no free movement, no going back into the EU.
"So the discussion about a close relationship with the EU, is in that context and within those frameworks.
"I'm convinced, and I think you heard from the chancellor himself, that we can have a close relationship, notwithstanding those clear red lines that we've got and we've always had."
Scholz said: "We want to create good relations between the UK and the European Union, it can become better day by day, and we all share an interest."
"[There is a] reason to do everything in our power to improve relations between both countries but also the UK and the European Union".
Following his engagements in Berlin, Starmer was heading to Paris for the start of the Paralympics and talks with French President Emmanuel Macron, where he will continue to pursue his reset agenda.
