EU Brexit negotiator Michel Barnier (R) and British Labour Party leader Jeremy Corbyn walk prior to a meeting on July 13, 2017 in Brussels | Pool photo by Olivier Hoslet/AFP via Getty Images UK should pay its ‘legally obliged’ Brexit bill, says Jeremy Corbyn The Labour leader also expressed skepticism that the UK could strike a quick trade deal with the US.

The U.K. should “pay what it is legally obliged to pay” in a Brexit divorce settlement and remain within Europe’s nuclear energy regulator Euratom, Labour leader Jeremy Corbyn said following a meeting with the EU’s chief Brexit negotiator Michel Barnier on Thursday.

Adopting a more conciliatory tone than Conservative ministers, Corbyn said he had not discussed a figure for the so-called Brexit bill during “frank” discussions in Brussels with Barnier but he recognized the U.K.'s role in funding EU infrastructure and development programs across Europe.

“We are clear that we will pay whatever we are legally obliged to pay and those EU funded programs in the U.K. that go beyond 2019 must also continue,” said the Labour leader, who underlined the phrase by repeating it three times during a press briefing.

He said the intention behind his visit to Brussels was to set out his party’s position on trade access and the rights of EU citizens living in the U.K. “The difference between us and the Conservatives is we are not threatening Europe,” he said.

The tone from the U.K. government has been much more combative over the Brexit bill. Foreign Secretary Boris Johnson told the House of Commons Tuesday the sums being mentioned were “extortionate and I think ‘to go whistle’ is an entirely appropriate expression.”

Speaking Wednesday, Barnier said it was important for Britain to show flexibility over the bill to build trust in the talks. “It is essential that the United Kingdom recognize the existence of financial obligations, which are simply the result of the period during which they were members of the European Union,” he said.

On Britain’s membership of the European Atomic Energy Community, or Euratom, Corbyn said it was crucial for regulations on the use of nuclear material to be harmonized across Europe.

“I would like us to stay in Euratom,” he said, “I suspect there are complications around that but there’s got to be an agreed form of regulation for the nuclear industry for obvious issues of nuclear power and nuclear fuels and reprocessing — but crucially also for medical treatment.”

The 60-year-old Euratom predates the EU and, among other things, makes sure countries don’t use their nuclear material for weapons; manages nuclear fuel supply; allows workers and equipment to move freely; and funds research and innovation. Some radioactive isotopes used in sophisticated medical diagnosis, for example for cancer treatment, cannot be made in the U.K. and are regulated by the organization.

MPs have expressed fears that leaving Euratom at the end of the two-year Brexit process in March 2019 would not leave enough time for the U.K. to replicate these vital functions.

Asked whether he would accept the jurisdiction of the European Court of Justice, which arbitrates in Euratom disputes, Corbyn said: “Our view is there has to be a judicial disputes resolution process of some sort which we would support because clearly if you are in an agreement on, say, transfer of radioisotopes in medicine, then you’ve got to have some means of arbitration.”

Likewise, on the question of whether the ECJ could be involved in enforcing an agreement on the rights of EU citizens in the U.K. post Brexit, the Labour leader did not insist, as the government does, that British courts can handle any disputes. But nor did he endorse the EU’s position that the ECJ must have jurisdiction.

“With any international agreement there has to be a process of arbitration somewhere,” he said, “we would accept and understand ... there has to be a dispute mechanism of some sort which has to be legally binding.”

On trade, Corbyn was skeptical that the U.K. would be able to do a trade deal with the United States "in the form that Donald Trump presented it." Prime Minister Theresa May discussed a trade deal with Trump on the fringes of the G20 summit in Hamburg Saturday, and Trump predicted a “very powerful” deal “very very quickly.”

But Corbyn said: “It’s very clear that trade relations have to be linked to other issues and if you have trade relations that insist on product quality, that insist on adherence to Paris climate accord — as the European trade arrangements do — then that’s incompatible with a deal with the United States in the form that Donald Trump presented it.”