US 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.
US 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.
US 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 unshakable 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.
British daily The Guardian reported on Friday that officials in key parts of the Obama administration are becoming increasingly convinced that sanctions cannot succeed in deterring Iran's nuclear aspirations and that the US will be forced to launch a military operation against Tehran or watch Israel do so.
"The White House wants to see sanctions work. This is not the Bush White House. It does not need another conflict...Its problem is that the guys in Tehran are behaving like sanctions don't matter, like their economy isn't collapsing, like Israel isn't going to do anything," The Guardian quoted an official familiar with Obama's Middle East policy as saying.
"Sanctions are all we've got to throw at the problem. If they fail then it's hard to see how we don't move to the 'in extremis' option," he added.