DUBAI: Iran and the United States have made some progress as they push for an agreement under Pakistani mediation, but more than halfway through a two-week truce big splits remain including over Tehran's nuclear ambitions, a senior Iranian official said on Thursday.

"The trip of the Pakistani army chief to Tehran was effective in reducing differences in some areas, but fundamental disagreements still remain in the nuclear field.... More hopes have been created for extending the ceasefire and holding a second round of talks," the senior official said.

"The fate of Iran’s highly enriched uranium and the duration of Iran’s nuclear restrictions are among the highly disputed issues for which no solution has yet been found."

Pakistan's army chief Field Marshal Asim Munir visited Tehran on Wednesday to try to prevent a renewal of the conflict. Pakistan hosted the war's first peace talks last weekend.

A spokesperson for Pakistan's Foreign Ministry said on Thursday that no dates have been decided for a second round of talks between the U.S. and Iran.

Iran and the United States failed last weekend to agree an end to the war that U.S. President Donald Trump launched alongside Israel with a surprise attack on February 28, triggering Iranian fire at Gulf states and igniting a parallel conflict in Lebanon.