Iran has officially notified the mediators that it does not want to meet the US envoy in Islamabad, reports the Wall Street Journal.
Iran considers US demands "unacceptable", according to mediators.
Turkey and Egypt are trying to get new talks underway. Possible locations for negotiations include Doha, the capital of Qatar, and Istanbul, Turkey.
In addition, new proposals are being aired to avoid the deadlock.
In the diplomatic rounds, Iran is said to be demanding that the US make several promises, including financial compensation, the withdrawal of US forces from bases in the Middle East, and a guarantee that the US will not attack Iran again.
