TEHRAN -- Iran has rejected a US proposal for a 48-hour ceasefire, the semi-official Fars news agency reported on Friday.

The proposal was delivered to Iran through a "friendly" country on Thursday, Fars quoted an informed source as saying.

The source added that Washington has stepped up its diplomatic efforts to secure a ceasefire, particularly after an Iranian strike targeted a US "military forces depot" on Kuwait's Bubiyan Island.

According to Fars, assessments suggest that the proposal was put forward following an intensification of the crisis in the region and "serious problems" for US forces resulting from their country's "miscalculation" of Iran's military capabilities.

The report added that Iran's response to the offer was not given in writing, but through the continuation of attacks in the battlefield.

On Feb 28, Israel and the United States launched joint attacks on Tehran and several other Iranian cities, killing Iran's then Supreme Leader Ali Khamenei, along with senior military commanders and civilians. Iran responded by launching waves of missile and drone strikes targeting Israel and US assets in the Middle East.