U.S. President Barack Obama's top security aide will visit Israel for two days of talks on regional issues including Syria and Iran, the White House said on Friday.

National security adviser Tom Donilon's trip from Saturday through Monday comes amid tensions over Iran's nuclear program, which the West says is aimed at securing weapons capability, but Tehran insists is for peaceful purposes.

U.S. and European officials on Friday voiced cautious optimism over the latest signals from Tehran that it might be willing to resume talks with major powers on the nuclear issue, after the Iranians sent them a letter.

Donilon's visit was "the latest in a series of regular, high-level consultations between the United States and Israel, consistent with our strong bilateral partnership, and part of our unshakeable commitment to Israel's security," the White House said in a statement.

Obama said earlier this month that he did not believe Israel had decided how to respond to its concerns about Iran's nuclear program, following public discussion within Israel about whether it should attack Tehran to stop it from getting a nuclear bomb.

In Syria, which borders Israel to the northeast, violence continued to rage on Friday despite international protest and the forces of Syrian President Bashar al-Assad renewed their attack on the opposition stronghold of Homs.