As Sir Keir Starmer marks one year as PM, he said he "understands what anchors" US President Donald Trump.
Sir Keir may share largely "different political backgrounds" with his US counterpart, the PM explained he found common ground with Trump.
He believes their "good personal relationship" helped secure the US tariff deal.
Sir Keir said that the US President reached out to console him following the death of his younger brother Nick Starmer on Boxing Day.
The PM added: "For both of us, we really care about family and there's a point of connection there.
"I think I do understand what anchors the president, what he really cares about."
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Sir Keir says he first spoke to Trump as PM after the then-presidential candidate was shot at a rally in July last year.
He said: "That was a phone call really to ask him how it was, and in particular I wanted to know how it impacted on his family."
Speaking to the BBC, Sir Keir denied claims the welfare reform U-turns were caused by being too focused on foreign affairs.
The legislation cleared its first hurdle by 335 votes to 260, majority 75.
However, Sir Keir was forced to abandon a key plank of his welfare reform package in the face of the rebellion.
A further concession was offered to rebel Labour MPs with just an hour to go before the vote.
Cuts to Personal Independence Payments – commonly known as PIP – will now not take place until after a review.
The PM admitted responsibility for the events, describing it as a "tough" few days but insisting the government would "come through this stronger" after a period of reflection.
Sir Keir said creating good relationships with political figures such as Trump and French President Emmanuel Macron were "always in the national interest".
He said these ties as "hugely important".
Sir Keir said his close ties with the US President had helped secure a deal removing UK industries from some of the controversial tariffs announced by Trump.
Before he cinched the deal, Sir Keir said he had seen how 'anxious' British factory workers at Jaguar Land Rover in Solihull were.
"After the deal, the relief was palpable," he said.
Meanwhile, Sir Keir said meeting Macron "over a glass of of wine" on a train to Kyiv had also helped bring forward a new agreement with the EU, which he claimed would result in lower food prices in British supermarkets.
"That is a good thing for millions of people across the country," he added.
