Some EU countries are pushing for the European Union's no-deal legislation to be more generous to the UK.
The European Commission has proposed "bare bones" arrangements on aviation and road haulage if there is no deal.
The legislation would allow British truckers to carry goods into the EU and British airlines to fly in and out of the EU, from 29 March to 31 December.
But a group of countries want to give UK hauliers the right to operate within the EU as well, known as cabotage.
Some also want British airlines to be able to offer connecting flights within the EU.
Diplomats are also concerned that airlines will not be able to offer new routes or run more services because the number of flights would be capped at 2018 levels.
Speaking on BBC Radio 4's Today programme, France's Finance Minister Bruno Le Maire said: "You can't be out of the EU and be getting the benefits of the single market."
"That is the clear red line of France."
The issues were discussed at a meeting of member states' ambassadors in Brussels on Wednesday.
Officials will try to hammer out a compromise at a meeting on Friday and ambassadors will discuss it again next week.
"We've got to strike a balance between being prepared but not sending the message to the UK that no deal would be OK," a diplomat said.
The European Commission, which co-ordinates planning for no deal at a European level, is opposed to expanding the scope of the legislation, saying it would give the UK some of the benefits of membership of the single market.
The commission also urged member states not to engage in bilateral deals with the UK, which some countries have suggested, because much of the responsibility for these issues rests with national governments.
Details of the discussion are contained in a diplomatic note of a meeting of EU ambassadors on Wednesday.
At least one country asked whether the EU should consider additional contingency measures to guarantee co-operation on security issues, such as the Schengen Information System which is used to share information about stolen goods and people of interest.
The news will cheer supporters of a no-deal Brexit, who argue that the EU would be prepared to offer mini-deals with the UK if the withdrawal agreement it has negotiated with the UK is not approved.