According to a translation from Al Jazeera Arabic, the US source said, "We do not rule out launching joint retaliatory strikes with Israel if it is attacked by Iran or its agents."

There was no further elaboration, or an indicator whether a US joint response with Israel would include offensive strikes against Iran, or if this would just be defensive, for example - anti air measures. However, Axios has the following details which appears to confirm the Al Jazeera reporting:

The senior U.S. military commander in charge of the Middle East is expected to go to Israel Thursday to coordinate around a possible attack on Israel by Iran and its proxies, two Israeli officials said.

...The commander of the U.S. military central command (CENTCOM) Gen. Erik Kurilla is expected to meet senior Israeli Defense Forces (IDF) officials and Israeli defense minister Yoav Gallant.

Yesterday, Israeli officials threatened that Iranian nuclear sites could be targeted, in one of the biggest strike threats to date. The region is on edge awaiting an 'imminent' response by Iran following the April 1st deadly attack on Iran's embassy in Damascus. US intelligence has said it believes a revenge attack from Tehran is coming soon.

And just like that what was already a terrible day for doves and those hoping disinflation would finally arrive - not to mention Biden and the Fed - got much worse when moments ago oil spiked by over $1 per barrel with WTI jumping above $86 and Brent over $90...