"I believe it's a good start. We're not there, we're beginning the process," Mohammad Javad Zarif told reporters after meeting his French, British and German counterparts in Brussels.

The three European signatories to the landmark 2015 deal are leading international efforts to preserve it after US President Donald Trump withdrew and reimposed sanctions lifted under the accord.

Tehran has said it wants guarantees that the economic benefits the deal brought will continue if it is to stick with it and Zarif warned he expected to see progress "within the next few weeks".

The EU has said it will stick to the deal as long as Iran does, but the Islamic republic has warned it is ready to resume "industrial-scale" uranium enrichment if it is not satisfied.

The deal, painstakingly negotiated over more than a decade, lifted punishing economic sanctions on Iran in return for it abandoning its nuclear ambitions.

Trump cast the agreement into jeopardy a week ago when he abruptly pulled the US out.