Netanyahu's government has always opposed a deal with Tehran over its nuclear programme, and he is to address the US Congress on March 3 on the subject, in a move that has angered the White House.
"The information which has reached me in recent days greatly strengthens our concerns regarding the agreement being formulated between the major powers and Iran," said a Netanyahu statement.
"This agreement, if indeed it is signed, will allow Iran to become a nuclear threshold state.
"It is my obligation as prime minister to do everything that I can to prevent this agreement. Therefore, I will go to Washington... because the American Congress is likely to be the final brake before the agreement."
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House Speaker John Boehner invited Netanyahu to address a joint session of Congress on March 3.
President Barack Obama has refused to meet Netanyahu during his trip, saying diplomatic protocol forbids him from doing so, since the Israeli leader is running for re-election on March 17.
The two leaders have a famously frosty relationship, which has grown even more tense as a result of the disagreement over Netanyahu's upcoming speech.
Britain, China, France, Russia, the United States and Germany -- known as the P5+1 -- have been seeking a comprehensive accord with Iran that would prevent Tehran from developing a nuclear bomb in return for an easing of economic sanctions.
Tehran says its nuclear programme is purely for civilian use.
There is a heightened sense of urgency as the clock ticks down towards a March 31 deadline to agree on a political framework for the deal.