US President Barack Obama called protecting Israel's security a "top priority" for the US when welcoming the first Israeli leader to visit his White House on Tuesday. Obama met with President Shimon Peres, after which Peres told reporters that "there is no space between us and the United States." But in a sign of the differences between the views of the two new governments, in an earlier meeting with Vice President Joseph Biden, Peres said ending natural growth in settlements was a non-starter. "Israel cannot instruct settlers in existing settlements not to have children or get married," Peres said. In comments before the American Israel Public Affairs Committee earlier in the day, Biden said that settlement expansion must stop, and called on Palestinians and the Arab world to make "meaningful gestures" to advance peace. Peres also rejected the idea of "linkage" between the Palestinian and Iranian issues, two topics the US administration has frequently mentioned together. The visit started with a 30-minute meeting among Peres, Israeli Ambassador to the US Sallai Meridor and Obama, along with several top aides, including National Security Council chairman Gen. James Jones. The two presidents then held a 15-minute tÃªte-Ã¡-tÃªte. Before his meeting with Obama, Peres said Israel hadn't demanded that the US set a time limit on its negotiations with Iran. "Israel doesn't give the US an ultimatum," he said in a briefing with Israeli reporters following his meeting with Secretary of State Hillary Clinton. He also said that the US and Israel were "100 percent" on the same page when it came to Iran, in response to a question from The Jerusalem Post. Though Israel has repeatedly expressed its concern that America's talks with Iran will last too long, allowing Teheran to master nuclear technology, Peres said the issue of a time frame was misleading. He explained that it was impossible to "set a clock," because events were "fluid and volatile" and would dictate the pace, instead of preset timelines. But earlier on Tuesday, Foreign Minister Avigdor Lieberman reportedly declared that action would need to be taken if three months of diplomacy elapsed with no results. Peres, who also met with US Speaker of the House Nancy Pelosi and Senate Foreign Relations Chairman John Kerry, described his meeting with Clinton as "excellent" and said there had been absolutely no tensions between the sides during the meeting. There has been much speculation about how the difference in stated US and Israeli policy - the US emphatically backs a Palestinian state, while the new Israeli government has avoided articulating that position - would play out in the initial meetings Israeli leaders are holding here in Washington. Peres's visit will be followed by that of Prime Minister Binyamin Netanyahu, on May 18. But Peres said he had emphasized that Israel accepted the road map peace plan, which calls for the eventual formation of a Palestinian state, and that the new government intended to keep to previous government decisions. "Repeating it again doesn't make it stronger," he said during the press briefing.