The UK prime minister told Germany's Angela Merkel she hoped this would lead to an increase in the "pace and intensity" of UK-EU negotiations.
As they met in Berlin, Ms Merkel said Brexit talks were at a "crucial phase".
She said that a political framework for future relations needed to be clear by October.
Their meeting came as Downing Street set out some of the detail of its new proposal for how trade between the UK and the EU could be handled after Brexit.
There are currently differing views within the cabinet about how closely the UK should stick to EU rules after Brexit, and what compromises should be made to achieve "as frictionless as possible" trade.
After months of tension and disagreement, the prime minster is gathering the entire cabinet at her country retreat, Chequers, on Friday with the aim of agreeing a UK proposal on how future relations should work.
That would then be the subject of negotiations with the EU - which might have different ideas.
The UK is due to leave the European Union at 23:00 GMT on 29 March 2019. But to allow time for parliaments in the UK and the EU to approve whatever deal is agreed, the aim is for the framework for future relations to be agreed this autumn.
According to No 10, the new plan would allow the UK the freedom to set its own tariffs on goods arriving into the country.
Technology would be used to determine where the goods will ultimately end up - and therefore whether UK or EU tariffs should be paid.
Downing Street says it is confident the arrangement would be partly in place by the end of the proposed transition period in December 2020 - with the system being fully operational by the next general election.
On regulations, it is understood that the UK would closely mirror the EU's rules - but Parliament would be able to decide where to deviate.
However, the arrangement has not been explained in full - and it is not clear whether the cabinet will back the plan, or whether the EU would agree.
A source close to Brexit Secretary David Davis refused to comment on report that he had already told Mrs May the plan was unworkable.
Mr Davis and Mrs May were "working closely on what will be presented on Friday", the source said.
