Canada on Monday called for "tough" sanctions to be maintained on Iran until it shows concrete signs of change over its nuclear program.

"Kind words, a smile and a charm offensive are not a substitute for real action," Canada's Foreign Minister John Baird told the UN General Assembly.

Baird said the international community has to remain cautious about calls for a nuclear accord made by Iran's President Hassan Rouhani.

"Nothing would make Canada more pleased than to see a change in Iran's nuclear ambitions. A change to its terrible human rights record. And an end to Iran's material support for terrorism," Baird told the annual UN summit.

"Now is the time for the global community to maintain tough sanctions against Iran in order that it take a different path on its nuclear program," he added.

Rouhani had a landmark conversation with US President Barack Obama and made several public statements that Iran does not seek a nuclear bomb in his visit to the UN last week.

Obama said better US-Iran relations are possible but also called for firm signs of change by the Iranian government which is under international sanctions over its refusal to halt uranium enrichment.