The International Road Transport Union (IRU) urged Switzerland on Tuesday to allow 40 tonne trucks to pass through the country as soon as it introduces its heavy goods vehicle tax on January 1.
The IRU argued that all elements of Switzerland's bilateral agreements with the European Union should be applied simultaneously.
Sören Rasmussen, head of the union's delegation at the EU, opposed what he said was the Swiss government's decision to apply the different elements of the bilateral accords with the EU in a piecemeal fashion.
The IRU said Switzerland should either introduce the tax as scheduled on January 1, and permit the trucks to start passing through Switzerland at the same time, or wait until the accords come in to effect in the middle of the year.
Switzerland is intending to go ahead with the introduction of a heavy goods vehicle tax, despite the failure of all the EU member states to ratify the accords before then.
José Bossard of the Swiss Integration Office, which is responsible for all aspects of European integration, told swissinfo: "The question of the lorries tax is primarily an internal matter for Switzerland."
"We don't need to be told when we can go ahead, we can introduce the levy in January, as scheduled. However, we will have to discuss the modalities with the EU beforehand."
The seven mainly commercial accords cover issues such as agricultural trade, and the free movement of people and research. Swiss citizens gave the treaties the go-ahead in a referendum in May, and since then government ministers have been rallying support for early ratification in European capitals.
swissinfo with agencies