The United States has prepared for what could be significant attacks on Israel by Iran or its proxies in the Middle East as soon as this week, White House national security spokesperson John Kirby said on Monday.

Kirby told reporters that the U.S. had increased its regional force posture in recent days and shared Israel's concerns about a possible Iranian-backed attack after Iran and Palestinian Islamist group Hamas accused Israel of carrying out the assassination of a Hamas leader in Tehran last month.

On Friday, the deputy commander of Iran's Islamic Revolutionary Guard Corps was quoted as saying by local news agencies that Iran was set to carry out an order by Supreme Leader Ayatollah Ali Khamenei to "harshly punish" Israel over the assassination on July 31 of Ismail Haniyeh in the Iranian capital.

Israeli Defence Minister Yoav Gallant told U.S. Defence Secretary Lloyd Austin on Sunday that Iran was making preparations for a large-scale military attack on Israel, Axios reporter Barak Ravid said in a post on X, formerly Twitter, citing a source with knowledge of the call.

In a statement on Monday, Gallant's ministry confirmed the call took place overnight. It said Gallant and Austin discussed operational and strategic co-ordination and the Israeli military's readiness in the face of Iranian threats.

Austin has ordered the deployment of a guided missile submarine to the Middle East. The U.S. military had already said it would deploy additional fighter jets and navy warships to the region to bolster Israeli defences.

Meanwhile, Prime Minister Justin Trudeau said Monday that there is a real risk of escalation in the conflict between Israel and Iran-backed, Lebanon-based Hezbollah militants, and he urged Canadians to leave Lebanon while it's possible because Ottawa may not be able to extricate everyone if the situation worsens.

"We see that the risk of escalation is real, the challenges in the region are significant," Trudeau told reporters in Ontario.

"We are making certain preparations to be able to support in the event that everything gets much, much worse, but the situation is so difficult that we may not be able to get all Canadians out."