A major US arms deal with Israel sends Iran a "very clear signal" that military action remains an option to stop it from going nuclear, US Defence Secretary Chuck Hagel said on Sunday.

Hagel's comments came shortly before his arrival in the Jewish state at the start of a six-day regional trip likely to be dominated by worries over Iran's nuclear programme and Syria's civil war.

Asked if a multi-billion dollar arms package with Israel was designed to convey a message that a military strike remains an option, he said: "I don't think there's any question that's another very clear signal to Iran".

The trip, his first to the region since taking over the Pentagon nearly two months ago, was likely to see Hagel putting the finishing touches on plans to sell $10 billion worth of advanced missiles and aircraft to Israel, the United Arab Emirates and Saudi Arabia in a bid to counter the threat posed by Iran.

The deal, which was unveiled on the eve of Hagel's departure, will see Israel obtaining anti-radiation missiles designed to take out enemy air defences, radar for fighter jets, aerial refuelling tankers and Osprey V-22 tilt-rotor transport aircraft.

It will also see the sale of US F-16 fighter jets to the United Arab Emirates and sophisticated missiles to Saudi Arabia.

American and Israeli leaders have been at odds over Iran, with President Barack Obama's administration arguing tough sanctions and diplomacy need to be given more time to work.

But Israel, believed to be the Middle East's sole if undeclared nuclear power, has repeatedly warned time is running out and has refused to rule out a pre-emptive military strike to prevent Iran from obtaining an atomic weapons capability.

Hagel insisted there was no rift between Israel and Washington over the threat posed by a nuclear Iran but conceded there were differences over the timing.

"I think it's clear.... that Israel and the United States see the threat of Iran exactly the same," he told reporters.

"So I don't think there's any daylight there. When you break down into the specifics of the timing of when and if Iran decides to pursue a nuclear weapon, there may well be some differences," he said.

Last week, Israel's Chief of Staff Lieutenant General Benny Gantz said the Israel Defence Forces were capable of attacking Iran on their own without US support.

But Hagel declined to be drawn on suggestions the Jewish state could act alone, only saying Israel was a sovereign nation which had "the right to defend itself, to protect itself".

And he said more time was needed to see if sanctions and diplomacy would convince Iran to change its course.

"I think our policy is the correct policy. Israel has every right to make its own assessments," he said, adding the two allies were "working very closely".

Hagel visited Yad Vashem in Jerusalem, Israel's memorial to the Jewish victims of the Holocaust, where he laid a wreath on the stone crypt containing the ashes of some of those who perished in Nazi concentration camps.

The painful truth of the Holocaust "is a reality," Hagel said. "It did happen. We must prepare our future generations in our time here for a clear understanding that we must never allow this to happen again."

During the visit, Hagel will hold talks with his Israeli counterpart Moshe Yaalon, Prime Minister Benjamin Netanyahu and President Shimon Peres before leaving for Jordan on Tuesday afternoon.

In his tour of the region, Hagel also will travel to Egypt, the United Arab Emirates and Saudi Arabia where he will discuss the final details of the arms deal.

Hagel's arrival in Israel marks the third visit by a top US official within the past month, coming hot on the heels of a trip by US Secretary of State John Kerry and a historic visit in March by Obama.

Before his appointment as defence secretary, Hagel -- a blunt-talking, fiercely independent Republican -- was accused by elements within his own party and in Israel for being being too soft on Iran and too tough on the Jewish state.