The Argentinian Rugby Union (UAR) had been hoping the Pumas would be allowed to take part in either of the prestigious tournaments within the next two or three years.
But Loffreda believes that prospect is unlikely and wants the UAR to devise a competition closer to home if the Pumas are to remain competitive in the international arena.
"It's very improbable that the Pumas to will ever play in these international competitions," he said.
"We have to quickly find a home-made solution to maintain our level. It is important we maintain the historic high-quality level of our players."
Argentina face a tough test of their credentials when they host South Africa in Velez Sarsfield on November 5.
They should be able to call upon their squad members who play in the British and French leagues but Loffreda - nicknamed "El Tano" - knows it will be a tough for his team to overcome a resurgent Springboks outfit.
"I saw South Africa perform very well in the recent Tri-Nations," he said. "They are one of the best teams of the world.
"I was told there have been arrangements made between the English and French Rugby Union boards, so we won't have any problems about player availability."