Obama's visit to Israel, from the start, has been designed to send a message of reassurance to a key ally.
At an extravagant welcoming ceremony, Obama sounded a message that "peace must come to the Holy Land" and that such a goal could not be achieved at Israel's expense. U.S. backing for Israel will be a constant as the Middle East roils with revolution and Iran continues work on its nuclear program, he said.
"The United States is proud to stand with you as your strongest ally and your greatest friend," Obama said after landing at Tel Aviv's Ben Gurion International Airport.
"Across this region the winds of change bring both promise and peril," he said, calling his visit "an opportunity to reaffirm the unbreakable bonds between our nations, to restate America's unwavering commitment to Israel's security, and to speak directly to the people of Israel and to your neighbors."
Seeking to alter a perception among many Israelis that his government has been less supportive of Israel than previous U.S. administrations, Obama declared the U.S.-Israeli alliance "eternal."
"It is forever," he said to applause as Israeli and U.S. flags fluttered in a steady breeze under clear, sunny skies.
Even before leaving the airport for Jerusalem, Obama offered a vivid display of the U.S. commitment to Israeli security by visiting a missile battery that is part of Israel's Iron Dome defense from militant rocket attacks. The United States has invested hundreds of millions of dollars in developing the system with Israel.
Obama and Netanyahu toured the battery, brought to the airport for the occasion. They met and chatted with soldiers who operate the system that Israel credits with intercepting hundreds of rockets during a round of fighting against Gaza militants last November.
Netanyahu, who sparred frequently with Obama over the course of the U.S. president's first term, praised the president.
"Thank you for standing by Israel at this time of historic change in the Middle East," he said. "Thank you for unequivocally affirming Israel's sovereign right to defend itself by itself against any threat."
Obama, who joked that he was "getting away from Congress" by visiting Israel, planned to visit several cultural and religious sites aimed at showing his understanding of the deep and ancient connections between the Jewish people and the land that is now Israel.
He will also meet Palestinian Authority President Mahmoud Abbas in the West Bank and travel to Jordan before returning home on Saturday.