WASHINGTON -- Israeli Prime Minister Benjamin Netanyahu told Congress on Tuesday that an emerging agreement between Iran and the United States would all but guarantee that Tehran gets nuclear weapons and would be a very bad deal, drawing an extraordinarily blunt rebuttal from President Barack Obama.

Netanyahu said "Iran has proven time and again that it cannot be trusted," no matter what it says about permitting verification of the terms of any accord designed to prevent it from getting a nuclear bomb.

"The greatest danger facing our world is the marriage of militant Islam with nuclear weapons," he said in remarks before a packed House chamber that drew loud applause from Republicans and a more restrained reaction from Democrats in an appearance that has stirred political controversy in two countries.

Obama saw it differently, and said so from the White House. He said that the Israeli leader offered no "viable alternatives" to the nuclear negotiations with Iran and that the prospect of an agreement had already resulted in a freeze and rolling back of Iran's program.