U.S. officials believe Israel has narrowed its targets in response to an Iranian missile attack on what those officials call Iran's military and energy infrastructure, NBC News reports.

There is no indication that Israel will strike nuclear facilities or carry out assassinations, but U.S. officials emphasized that the Israelis have not yet made a final decision on how and when to act.

Officials said Israel has shared more information with the U.S. about retaliatory measures, but they have withheld many details for operational security reasons. The US is prepared to protect its assets in the region from any immediate counterattack by Iran, but is unlikely to provide direct military support for the operation, the media outlet said.

US Defense Secretary Lloyd Austin spoke with his Israeli counterpart Yoav Gallant last night and they discussed Israel's response in general terms. However, it is not clear whether Gallant provided any specific details.

According to U.S. officials, President Joe Biden and Prime Minister Benjamin Netanyahu also did not discuss details during a phone call this week.