The United States plans to bolster an Israeli anti-rocket system with $70 million in assistance this year and more funding is likely in the future, Defense Secretary Leon Panetta said Thursday.

The "Iron Dome" air defense network has been credited with thwarting Palestinian militant rocket and mortar attacks out of Gaza.

"My goal is to ensure Israel has the funding it needs each year to produce these batteries that can protect its citizens," the Pentagon chief said in a statement after meeting with his Israeli counterpart, Ehud Barak.

"That is why going forward over the next three years, we intend to request additional funding for Iron Dome, based on an annual assessment of Israeli security requirements against an evolving threat," the statement also quoted Panetta as saying.

The announcement fell short of predictions published in Israel's Haaretz daily that Washington was ready to commit to $680 million to pay for more anti-rocket batteries over several years.

Instead, the US administration chose to provide $70 million for the current year and review the issue in future years, allowing some potential leverage over Israel.

US-Israeli relations have been strained over how to counter Iran's nuclear program, with Washington arguing that sanctions need to be given a chance to work while Israeli leaders have suggested time is running out and that unilateral military action may soon be necessary.

Panetta called the aid for the air defense system "part of our rock solid commitment to Israel's security," which comes "on top of approximately $3 billion in annual security assistance."

The Pentagon has already delivered $205 million in assistance for the Iron Dome system.

Panetta added that "we will stay in close consultation in the years ahead to ensure we are making necessary investments in this important system."

Barak's visit to Washington was the third in as many months and came as the United States and other major powers prepared for a fresh round talks this month with Iran on its nuclear program.

In recent weeks, Israel has launched a diplomatic offensive to drive home its concerns to world powers in advance of the May 23 talks in Baghdad.

Barak warned on Monday that the United States and other powers were only making "minimalist" demands of Iran that would fail to persuade Tehran to halt its disputed nuclear drive.

But a commentary published Thursday by former spy chiefs from Germany, Israel and the United States as well as other ex-officials argued that there was still time for sanctions to work. The authors called for ratcheting up punitive measures designed to fully deny Iran access to foreign banks, international shipping and foreign insurance companies.

"It is still in Iran's interest to change course and address international concerns regarding possible military aspects of its nuclear program," the authors wrote in the Wall Street Journal.

"Our rationale is based on strong empirical evidence from the last few months that sanctions are having a tangible impact."

Israel and most of the West believe Iran's nuclear energy program masks a drive to develop atomic weapons. Tehran denies such intentions.