If we try to play for time, she said, our problems will worsen and won't become easier. Avoiding tough decisions is the strategic threat on Israel's future, she added.
The Kadima chairwoman noted that her role as opposition leader was to say these things out loud, clearly and in a respectable manner, for the State of Israel. "If we care about the future of our people in our homeland we will all find the courage and the wisdom to make the choices we can no longer afford to avoid," she said.
Speaking for the first time in the United States since assuming the role of opposition leader, Livni said that "on the issue of Iran - there is no opposition party in Israel."
She stressed that Israel was united in understanding the threat and would work together with the free world in order to prevent Iran from obtaining the ability to threaten the region and the world with nuclear weapons or terror.
She stressed, however, the possibility of cooperating with some Arab countries. Leaders' role is to see not only the threats but also the opportunities, she said, adding that the Iranian threat has created new opportunities for alliances between Israel and the region's moderate countries, which have learned that Israel was not the source of trouble in the Middle East.
Today more than ever, she said, the need to confront Iran is being heard in Arabic as well and not just in Hebrew. She added, however, that she would like the Arab voices to be stronger.
'Arab states must confront extremists'
Livni went on to say that Israel and the Palestinians were not the only ones responsible for taking risks for peace, but that the Arab states must do that as well. She urged them to begin a process which she called "normalization in stages".
According to the opposition leader, the Arab countries must confront the extremists and use the historic Arab peace initiative not as an alternative for negotiations, but as a framework for supporting the Palestinians, who will be forced to deal with painful concessions.
The burden of proof, according to Livni, belongs to the Arab leaders. "We need them to prove to a justly skeptical Israeli public, that peace will offer Israel strategic benefits across the Middle East; and allow Israel to take its rightful place as an integral part of the region.
"I know that some of these pragmatic states claim that we must resolve the Israeli-Palestinian conflict before they can actively join the efforts against the extremists in our region. There are others, including some in Israel, for whom the existence of the threat is an excuse to avoid taking the difficult steps needed to advance coexistence. I do not accept either view."
The former foreign minister argued that advancing peace between Israel and its neighbors was not something the Israelis should be afraid of. We are not doing a favor to the Palestinians or the Arab world or not even to the American administration, she said.
Livni vowed that Israel would remain a Jewish and democratic country forever. Time is not in our favor, she added.
Earlier, the opposition leader met with the White House's chief of staff, Rahm Emanuel. On Monday she is expected to visit the White House for a meeting with National Security Advisor Jim Jones.