Negotiating teams from the U.S. and Iran could return to Pakistan later this week to resume talks on ending the Middle East war, Pakistani and Iranian officials said Tuesday, just days after the first round of peace talks ended without a breakthrough.

There was no immediate confirmation from U.S. officials about the plans, which the Iranian and Pakistani officials discussed on condition of anonymity.

A source who has been involved in the talks said a proposal had been sent to Washington and Tehran for the delegations to return to Islamabad to resume discussions.

No date had yet been decided, but both countries could return as early as the end of this week.

An official at the Iranian embassy in Islamabad said: "The coming rounds of talks can come sometime later this week or earlier next week. But nothing is finalised as of now."