"As Israel says goodbye to prime minister Sharon, we join with the Israeli people in honouring his commitment to his country," Xinhua reported citing Obama in a statement.
Sharon died at a hospital in central Israel Saturday after eight years in coma. He was 85.
"We reaffirm our unshakable commitment to Israel's security and our appreciation for the enduring friendship between our two countries and our two peoples," Obama said.
Ariel Sharon died at a hospital on Saturday after eight years in coma
He said the US continues to strive for lasting peace and security for the Israelis, including through the country 's commitment to the goal of two states living side-by-side in peace and security.
US Vice President Joe Biden said in a statement that he was "saddened" to hear Sharon's passing and sent condolences to Sharon's family and to the Israeli nation.
Biden will lead a US delegation to Sharon's memorial service to pay respects to the leader and pay tribute to the unshakable partnership between the US and Israel.
US Secretary of State John Kerry said America shares the loss of the Sharon family and the Israeli people and honours the leader's memory.
"He was prepared to make tough decisions because he knew that his responsibility to his people was both to ensure their security and to give every chance to the hope that they could live in peace, " Kerry said in a statement.