Israeli Prime Minister Benjamin Netanyahu on Monday called for "a clear and credible military threat" against Iran, saying the Islamic republic is getting closer to building a nuclear bomb.

The hawkish Israeli leader, told a pro-Israel lobby group in Washington via satellite link from Jerusalem that diplomacy and sanctions have not worked to stop Iran from pressing ahead with its controversial nuclear program.

"Iran enriches more and more uranium, it installs faster and faster centrifuges," Netanyahu told the American Israel Public Affairs Committee policy conference.

"It's still not crossed the red line I drew with the United Nations last September, but Iran is getting closer to that red line and it's putting itself in a position to cross that line very quickly once it decides to do so," he said.

Washington and its allies have imposed crippling sanctions on Iran over the years on top of tough measures adopted by the UN Security Council, and Iran has agreed to have more talks with the so-called P5+1 group of Britain, China, France, Russia, the United States and Germany this and next month after their talks in Kazakh city of Almaty produced positive results last week.

However, Netanyahu claimed that Iran used negotiations to "buy time" for its nuclear program, saying "so far the sanctions have not stopped the nuclear program either."

"Words alone will not stop Iran. Sanctions alone will not stop Iran. Sanctions must be coupled with a clear and credible military threat if diplomacy and sanctions fail," he said to loud cheers.

The prime minister said he would discuss Iran's nuclear project with U.S. President Barack Obama when he visits Israel later this month, along with issues relating to conflicts in Syria and peacemaking with the Palestinians.

The Obama administration prefers a diplomatic resolution to Iran's nuclear program, which the republic insists is for peaceful purposes only, and refused to set a red line for military strikes as requested by Netanyahu.