President Obama is not backing down on how to solve the Israel-Palestine border issue in achieving peace in the Middle East.

Speaking Sunday to the American Israel Public Affairs Committee – which identifies itself as America's leading pro-Israel lobby – Obama reiterated his stance: Any negotiation has to begin by acknowledging the 1967 borders before the Six-Day War in which Israel occupied land in Jordan, Syria, and Egypt.

In his closely-watched speech on the Middle East Thursday, Obama had made it clear that this had to include “mutually agreed swaps, so that secure and recognized borders are established for both states.”

But to Israeli Prime Minister Benjamin Netanyahu, many supporters of Israel, and Republican presidential hopefuls this was a nonstarter.

Israel “cannot go back to the 1967 lines,” the Israeli leader said. “Those lines are indefensible.”

Speaking to AIPAC Sunday, Obama sought to clarify what he had meant on Thursday regarding the 1967 borders.

“By definition, it means that the parties themselves – Israelis and Palestinians – will negotiate a border that is different than the one that existed on June 4, 1967,” Obama said. “It allows the parties themselves to account for the changes that have taken place over the last 44 years. It allows the parties themselves to take account of those changes, including the new demographic realities on the ground, and the needs of both sides.”

“The ultimate goal is two states for two people,” he said, “Israel as a Jewish state and the homeland for the Jewish people – and the State of Palestine as the homeland for the Palestinian people – each state in joined self-determination, mutual recognition, and peace.”

Other officials elaborated.

"The president didn't say that Israel has to go back to the '67 lines. He said with agreed swaps," former Middle East envoy George Mitchell said Sunday on ABC’s This Week. "Swaps means an exchange of land intended to accommodate major Israeli population centers to be incorporated into Israel and Israel's security needs. ‘Agreed’ means through negotiations. Both parties must agree."

"That's not going to be a border unless Israel agrees to it and we know they won't agree unless their security needs are satisfied, as it should be," Mitchell said.

In some sense, Obama is taking a risk in urging Israel to negotiate with Palestinian leaders – especially at a time when that leadership now includes Hamas, which the United States and some other countries consider to be a terrorist organization. It’s an issue that has bedeviled presidents before him.

But Obama also warns that “the current situation in the Middle East does not allow for procrastination.”

“The world is moving too fast,” he said Sunday. “The extraordinary challenges facing Israel will only grow. Delay will undermine Israel’s security and the peace that the Israeli people deserve.”

There’s a strong political dimension to what some see as a dilemma for Obama: Look for a breakthrough in the Israel-Palestine problem at a time when much of the region is in turmoil while also keeping the support of a key part of his political base.

In 2008, Obama won nearly 78 percent of the Jewish vote, and more than ever Jewish voters remain a crucial part of his political base – in terms of campaign contributions as well as votes.

In the end, much of what he said to AIPAC was greeted with applause – especially the introductory line of the organization president Lee Rosenberg: “Thank you Mr. President for ridding the world of Osama bin Laden.”

Responding to Obama’s assertion that “the commitment of the United States to the security of Israel is ironclad,” Netanyahu seemed to soften his position.

In a statement Sunday he said: “I am a partner to President Obama's wish to promote peace, and I appreciate his efforts in the past and present to achieve this goal. I am determined to work with President Obama to find ways to renew peace talks.”

The Israeli Prime Minister’s position will become clearer when he addresses AIPAC Monday night.