The organization provides essential services for over 5.3 million refugees in Gaza, the West Bank, east Jerusalem, Jordan, Lebanon and Syria.
The group had requested, but failed to receive a meeting with Mogherini.
The EU transformed itself into an Iranian tool after the Trump administration rejected its calls to receive exemptions from the new financial penalties.
Khan al-Ahmar was illegally built on state land. Its pending demolition has garnered international attention.
Tehran is threatening to withdraw from the deal unless Europe can guarantee it the economic benefits and protections that were built into the nuclear agreement.
Mogherini was originally scheduled to address the forum on Monday.
The continent has been anything but unified on the situation that unfolded on the Israel-Gaza border this spring.
EU High Representative Federica Mogherini urged a political process for peace in Syria while admitting that “the times are not encouraging” and that what was happening was “almost a disaster.”
UNRWA spokesman Chris Gunness said the budget deficit for 2018 is $446m.