By Parisa Hafezi

DUBAI, April 11 (Reuters) - A senior Iranian source said on Saturday the U.S. had agreed to release Iranian frozen assets that were held in Qatar and other foreign banks, welcoming the move as a sign of "seriousness" in reaching a deal with Washington in talks in Islamabad.

The United States has not made any public comments on the issue of unfreezing assets.

The source, who declined to be named due to the sensitivity of the matter, told Reuters that unfreezing the assets was "directly linked to ensuring safe passage through Strait of Hormuz", which is expected to be a key issue in the talks.

(Writing by Parisa Hafezi; Editing by Jan Harvey)