Speaking to Yle, Tuomioja added the US had informed that it needed extra time to consider the issue. After this, Russia and other nations took the same position.
Tuomioja is confident moves to reach agreement on an arms trade treaty will continue either at the UN General assembly in the autumn or in another forum.
He considered the draft treaty, supported by almost all states, to be good. Under its terms, nations signing up to the deal would ban the sale of conventional weapons to countries where they might be used to commit human rights violations or war crimes.
Finland is one of the countries behind the initiative for a binding multilateral treaty to regulate arms trade.