Image copyright Getty Images
The EU and UK's Brexit negotiators have said progress has been made, but "obstacles" remain before reaching a deal in October.
Speaking after talks with new UK Brexit Secretary Dominic Raab, Michel Barnier stated that Theresa May's Brexit White Paper plan was a "real step forward".
He highlighted agreement on security measures and said both sides wanted a wide-ranging free trade deal.
But he also said: "To be frank, we are not at the end of the road yet."
Mr Raab said: "We have agreed to meet again in mid-August and then to continue weekly discussions to clear away all the obstacles that line our path, to a strong deal in Octoberone that works for both sides."
He replaced David Davis, who quit as Brexit secretary in protest at Theresa May's plans for a future economic relationship between the UK and EU, as set out in the White Paper.
That set out in more detail the government's proposed customs system, the Facilitated Customs Arrangement for goods and agri-foods, where it plans for the UK to collect some EU tariffs.
But Mr Barnier said retaining control of the money, law and borders also applied to the EU's customs policy.
"The EU cannot and the EU will not delegate the application of its customs policy and and rules and VAT and excises duty collection to a non-member who would not be subject to the EU's governance structures," he said.
Any customs arrangement or union "must respect this principle", he said.
While UK proposals on security marked "a real step forward" and he welcomed the acknowledgement that the European Court of Justice was the only arbiter of EU law, he also said: "In contrast, on our future economic relationship, it comes as no surprise that finding common ground between the EU27 and the UK is more difficult."
Mr Raab said he and Mr Barnier would next meet in mid-August and would hold weekly meetings after that in an attempt to get a deal in place by October.
The UK Brexit Secretary said: "We have designed our proposals both to respect the result of the referendum, and the core principles of the EU.
"We have considered the innovative approaches the EU has taken in the past with other third countrieswhen the political will has been there.
"In sum, the UK has set out our plans in detail. Those plans are ambitious, principled and pragmatic. I am committed to injecting new energy into these talks, along with Michel."
Turning to Mr Barnier, he said: "Michel, we have work to do."
The UK is due to leave the EU on 29 March 2019 but has yet to agree how its final relationship with the bloc will work.