WASHINGTON, Oct 18 (Reuters) - The United States has concerns about some of the 477 Palestinians Israel freed on Tuesday in exchange for an abducted Israeli soldier because they killed or injured U.S. citizens, a U.S. official said.

The U.S. official, who spoke on condition of anonymity, said the Obama administration had conveyed its concerns to the Israeli government, suggesting it did so at the 11th hour as Israel engineered the swap to free Sergeant Gilad Shalit.

In one of the biggest such exchanges between Israel and the Palestinians, Shalit was freed after being held incommunicado for five years by Hamas, the Islamist Palestinian faction that rules the Gaza Strip and that vies for primacy with Fateh, which exercises limited self-rule in the West Bank.

In the deal with Hamas, which the United States regards as a foreign terrorist organization, Israel plans to free more than 1,000 Palestinian prisoners, the first 477 of whom left Israeli jails on Tuesday for Gaza, the West Bank and abroad.

State Department spokesman Mark Toner told reporters that the United States had concerns about some of the Palestinians whose release was envisaged in the deal but he would not specify whether any of these were among the 477 already freed.

As a matter of principle, the United States opposes the release of individuals who have been convicted of crimes against Americans, he said in an email.

We communicated our position to the government of Israel after we became aware of specific individuals who were identified as part of this release, he added.

The White House said President Barack Obama is pleased that Shalit has been freed and he wants Israelis and Palestinians to take steps toward resuming peace negotiations.

White House spokesman Jay Carney told reporters during the president's bus tour in North Carolina that it was not yet clear how Shalit's release would impact the Middle East peace process but said Obama was personally pleased by the development.

Each side needs to take steps that make it easier to return to negotiations rather than harder, Carney said.

While leaders of Islamist Hamas and their secular rivals in President Mahmoud Abbas's Fateh movement made conciliatory comments about each other's role in achieving the deal, it appeared likely to accentuate the divide between the factions.

Abbas is shunned by Hamas as a pawn of Israel and its Western allies but has angered Israel and the United States by refusing to revive long-stalled peace talks with the Israelis and by seeking full Palestinian membership in the United Nations.

(Reporting by Arshad Mohammed; Editing by Will Dunham)