The United States State Department said on Thursday it was confident there had been no security breach in the talks between Iran and six world powers, AFP reports.
Spokesman Jeff Rathke told reporters that the government was aware of the investigations that had been opened, and that Washington had "close working relationships" with both countries.
"We've taken steps throughout the negotiations to ensure that confidential details and discussions remain behind closed doors," Rathke said, according to the news agency.
The comments come after The Wall Street Journal reported on Wednesday that Israel attempted to use a sophisticated virus to spy on nuclear talks between Iran and P5+1 by hacking into the servers of hotels where talks were being held.
Cybersecurity firm Kaspersky Lab ZAO found the hotels on a list of European servers hacked by the virus, identified as a version of Duqu, while scanning its own systems after finding it had been hacked.
Thousands of other hotels were clean, it told the newspaper, and the firm later deduced that the nuclear talks were the only common denominator for the luxury hotels.
Swiss and Austrian investigators are separately looking into the report, according to AFP. The Swiss attorney general's office said it had seized computer equipment on "suspicion of illegal intelligence services operating in Switzerland."
Israel vehemently denied the report, with Deputy Defense Minister Rabbi Eli Ben-Dahan calling the allegations “utter nonsense. Israel does not use such methods, and we already have sufficient methods to find out what is going on in the talks” without having to resort to hacking.
Deputy Foreign Minister Tzipi Hotovely also denied that Israel spied on the talks.
Late Wednesday, a senior administration official said Washington had "terrific capabilities to try to ensure security" but cautioned, "Nothing ever stays completely secret in this world we live in these days."