Brussels - British Prime Minister Boris Johnson acknowledged on Monday that reaching a new withdrawal deal with the European Union will be a challenge as there was "substantial disagreement" between the two sides, but said he remained committed to trying.
Johnson also clashed with EU officials over whether Britain must pay the so-called divorce bill agreed with the EU in negotiations over the past few years - even in the event of a no-deal Brexit.
In his first press conference since becoming prime minister, Johnson reiterated comments from the weekend, suggesting that Britain would not be required to transfer 39 billion pounds (48 billion dollars) owed to the EU - a sum agreed under his predecessor Theresa May.
"Substantial sums will be available from the 39 billion [pounds] from the UK to spend on our priorities, including managing that no-deal scenario," he told reporters following the G7 summit in Biarritz, France.
The European Commission earlier Monday said EU member states were expected to honour their commitments, and this is "especially true in a no-deal scenario, where the UK would be expected to continue to honour all commitments made during EU membership," European Commission spokesperson Mina Andreeva said in Brussels.
Rather than being forced into legal action, the EU's Andreeva said "it is important to make clear that settling accounts is essential to starting off a new relationship on the right foot based on mutual trust."
If the UK doesn't pay what is due, the EU will not negotiate a trade deal.
Guy Verhofstadt, the Brexit coordinator in the European Parliament, went further: "If the UK doesn't pay what is due, the EU will not negotiate a trade deal. After a 'no deal,' this will be a first condition of any talks. Britain is better than this."
Johnson has vowed to take Britain out of the European Union by October 31, with or without a deal. He has demanded that any withdrawal deal remove the controversial Irish "backstop" provision that was meant as an insurance policy to prevent a border between Ireland and Northern Ireland from being re-established.
US President Donald Trump in his own press conference on Monday suggested a no-deal Brexit was likely, telling reporters that he had warned Johnson the EU is "a very strong group of people. They have their ideas and they're not easy to deal with, I can tell you."
Asked about the comments, Johnson replied that "everybody is a tough negotiator... but that doesn't mean we won't do a deal and we're working very hard to do that." He added: "It will be difficult. There is a substantial disagreement."
Still, Johnson said he was "marginally more optimistic" after meetings this week with his French, German and other counterparts. "It all depends on how seriously they wish to get a deal," he said.
Asked about trade negotiations with other countries, including the US, Johnson said he would prefer to reach a "comprehensive deal" rather than a quick deal that did not include vital elements like the services sector.