Three days before the Israeli and US leaders meet to discuss Iran’s nuclear programme, both men have set out their countries’ positions.
Barack Obama said he was not bluffing when he said it was unacceptable for Iran to have a nuclear weapon.
Israel’s prime minister Benyamin Netanyahu ruled out international talks to prevent Iran developing atomic weapons, as the US is pursuing a diplomatic solution.
The pair meet on Monday to discuss growing differences between the two over Iran, especially fears in Washington of a possible Israeli attack.
Obama told The Atlantic magazine that a military option was still one possibility among a package of other measures.
Israel’s defence minister Ehud Barak paved the way for the heads of state by meeting the US Defense Secretary Leon Panetta earlier in the week.
Both countries fear Tehran is using its nuclear programme for military ends. Iran has always maintained it is for peaceful purposes.