A senior Israeli official traveling in Netanyahu's delegation, who was not authorized to speak on the record, said the Israeli government had "a good understanding of the agreement we can draw conclusions from."
"We know what we know. And believe me, we know a lot of information about this agreement," the official told reporters aboard the flight to Washington. "The Prime Minister is going to Congress to explain what they don't know about this agreement that it is a bad agreement."
The official said Congress has "no understanding" of the deal shaping up. He described the Prime Minister's speech as a "last chance" to speak directly to Congress before a March 24 deadline for a political framework agreement about the elements believed to be in the deal.
The official would not disclose how the Israeli government reportedly had more information on the deal than the U.S. Congress, but noted that many of the parties were leaking details of the talks. However, in congressional testimony before a Senate Appropriations subcommittee last week, Secretary of State John Kerry said, "Anybody running around right now jumping in to say, 'Well, we don't like the deal' or this or that, doesn't know what the deal is. There is no deal yet. And I caution people to wait and see what these negotiations produce."
The official suggested Netanyahu would urge lawmakers in his Tuesday address to pressure the Obama administration to push the deadline so more discussion can take place about what he perceives is a dangerous deal that leaves Iran with the ability to develop a nuclear weapon down the line.
"There is no sacred date," the official said of the March 24 deadline. "It can be put off. It is not fixed. They can change it"
The official said that as the March 24 deadline approaches, Netanyahu will warn "be careful of giving up compromises. They are compromises and they are not good."
Obama hinted last week that he did not see the need for any additional extensions, saying the talks have, "sufficiently narrowed and sufficiently clarified that we're at the point where they need to make a decision."
That deadline was agreed to by the five parties and Iran, which is why Kerry is having marathon meetings with the Iranian Foreign Minister Mohammad Javad Zarif in Geneva beginning again this week.
Netanyahu spoke with Kerry on the eve of his trip, the official said, adding that despite the fraught political tone of Netanyahu's visit, the United States and Israel continue to communicate through intelligence channels. Intelligence and national security officials, this official said, met last week with National Security Adviser Susan Rice and Wendy Sherman, the lead U.S. negotiator for the Iran talks.
"The objective of Israel is to get a better agreement," the official said. "We want a good agreement. We are not against all agreements and the Prime Minister never said we were."