The US had seen Iran moving military assets, such as drones and cruise missiles internally, two US intelligence sources told CNN.
This is the latest development signaling a possible Iranian attack on Israeli targets, including targets within Israeli territory.
However, the sources say that it remained unclear whether or not Iran will attack from its own territory.
Iran could involve proxies in attack
According to US reports, Iran could also involve its proxies in carrying out such attacks.
The Biden administration asked Israel to update and consult with the United States before any Israeli response to a potential Iranian attack, senior American and Israeli officials said.
Iran was expected to attack Israel between the next 24 to 48 hours, the Wall Street Journal reported on Thursday, adding that the Jewish state is "preparing for a direct attack" on the north or south of the country.
This is a developing story.