A senior US government official says Iran could do something this week to retaliate against Israel for the killing of the top Hamas political leader, Ismail Haniyeh.

Iran vowed to take revenge on Israel after Haniyeh was killed last month while visiting Iran.

White House national security spokesperson John Kirby told reporters on Monday that US officials share the assessment made by their Israeli counterparts that "something could happen as soon as this week by Iran and its proxies."

He said that the US assessment matches the Israeli assessment.

He also said that it is difficult to ascertain at this particular time what their attack could look like.

Kirby stressed the need to prepare for what could be a significant set of attacks.

The United States and other countries mediating between Israel and Hamas are urging the two sides to resume ceasefire and hostage release negotiations on August 15.

Kirby said that "if something does happen this week, the timing of it could certainly well have an impact on these talks."

In light of mounting concerns about a possible retaliatory attack against Israel, US Defense Secretary Lloyd Austin has ordered the Navy to accelerate plans to send an aircraft carrier strike group to the Middle East. That will be added to another strike group already deployed in the region.