Iran said Thursday that the fragile Middle East cease-fire had become "practically meaningless" after renewed U.S. strikes and Iranian retaliation, further straining diplomatic efforts to contain the widening conflict, according to state media and official statements.

The war, which began on Feb. 28 with a wave of U.S.-Israeli strikes on Iran, was paused by the April truce, but efforts to hammer out a permanent end to the fighting have stalled and sporadic exchanges of fire have put the cease-fire under repeated strain.

In their second straight day of tit-for-tat attacks, Washington hit surveillance, communications and air defense facilities, U.S. Central Command (CENTCOM) said, while Iran's Revolutionary Guards announced a "punitive operation" targeting a U.S. base in Jordan and Gulf states reported incoming fire.

Mediators Pakistan and Qatar suggested backchannel efforts to negotiate an end to the war were ongoing despite the flare-up, though Islamabad cautioned it was "hard to be an optimist" in light of the latest escalation.

The strikes took place while a Qatari delegation was in Tehran for talks, with a diplomatic source saying the discussions lasted into the early hours of the morning and were "conducted in coordination with the United States."