U.S. President Barack Obama told visiting Israeli Prime Minister Benjamin Netanyahu that he has a “rock solid” commitment to Israel's security as the two leaders met to discuss how to prevent Iran from becoming a nuclear-armed state.

Speaking to reporters Monday in the White House before beginning private talks, Mr. Obama said he expects a series of “difficult months” this year as the United States and Israel coordinate their response to Iran's nuclear activities. Iran denies pursuing an atomic weapons program and says its nuclear ambitions are peaceful.

Mr. Obama said there is “still a window” to resolve the Iranian nuclear dispute diplomatically — an outcome that he said both he and Mr. Netanyahu prefer. But, the president reiterated his position that all options are on the table for stopping Iran from obtaining a nuclear weapon.

Mr. Netanyahu said Israel must reserve the right to defend itself and be the master of its own fate. He also expressed appreciation for the U.S. alliance with Israel and said both nations face a common enemy in Iran.

U.S. and Israeli officials have expressed differing views about what might trigger military action against Iran's nuclear sites. U.S. officials have said Washington may act if Iran makes a decision to assemble a nuclear bomb, while Israeli officials have said military action may be needed sooner, to prevent Iran from putting the pieces of a bomb beyond the reach of an attack.

In a speech to the American Israel Public Affairs Committee in Washington Sunday, Mr. Obama said the United States and Israel should give more time for diplomatic and economic pressure on Iran to “sink in.” He cautioned against what he called “too much loose talk of war” with Iran, but also said he is prepared to use military action if all other options fail.