Netanyahu said Iran had completed the first stage of uranium enrichment.
"Iran is 70 percent of the way there and ... well into the second stage. By next summer, at current enrichment rates, they will have finished the medium enrichment and move on to the final stage," Netanyahu said. "From there it is only a few more weeks before they have enriched enough for a bomb."
Netanyahu has repeatedly argued that time is running out to stop the Islamic Republic from becoming a nuclear power and the threat of force must be seriously considered.
"I believe that faced with a clear red line, Iran will back down and it will give more time for sanctions and diplomacy," the Israeli prime minister said.
Israeli leaders have issued a series of warnings in recent weeks suggesting that if Iran's uranium enrichment program continues it may soon stage a unilateral military strike, flouting even American wishes.
The Obama administration has urgently sought to hold off Israeli military action, which would likely result in the U.S. being pulled into a conflict and cause region-wide mayhem on the eve of American elections.
Israel considers a nuclear-armed Iran to be an existential threat, citing Iranian denials of the Holocaust, its calls for Israel's destruction, its development of missiles capable of striking the Jewish state and its support for hostile Arab militant groups.
"Given this record of Iranian aggression without nuclear weapons, just imagine Iranian aggression with nuclear weapons," Netanyahu said.