GENEVA -- U.S. Secretary of State John Kerry is warning that public discussion of details of the ongoing nuclear negotiations with Iran will make it more difficult to reach a deal that prevents the country from developing atomic weapons.

In comments to reporters in Geneva on Monday, Kerry said he was concerned by reports that some details of the talks would be revealed in coming days. He did not elaborate, but Israeli Prime Minister Benjamin Netanyahu will speak in opposition to a potential Iran deal in an address to Congress on Tuesday. Israeli officials say Netanyahu plans to discuss elements of the negotiations that he finds problematic and dangerous to Israel. Although Kerry did not identify Netanyahu as someone who might talk about details of the negotiations, he strongly hinted that was the case.

"We are concerned by reports that suggest selected details of the ongoing negotiations will be discussed publicly in the coming days," Kerry said. "I want to say clearly, doing so would make it more difficult to reach the goal that Israel and others say they share in order to get a good deal. Israel's security is absolutely at the forefront of all our minds but rightly so is the security of all the other countries in the region, so is our security in the United States."

Kerry's comments were unprompted by any question and came in his prepared opening remarks to a press conference after he delivered a speech defending Israel at the UN Human Rights Council.

Immediately after the press conference, Kerry headed to nearby Montreux, Switzerland to begin a new round of nuclear negotiations with Iranian Foreign Minister Mohammed Javad Zarif. Those talks are expected to last until Wednesday and will be underway when Netanyahu speaks in Washington to both the America Israel Public Affairs Committee on Monday and Congress on Tuesday.

Kerry cited "some progress" in the talks as negotiators bear down in trying to reach an end of March target to reach the outline of a final deal that they want by July.

But, he also said much more work was needed to ensure that all possible pathways for Iran to develop a nuclear weapon are verifiably closed off.

"Right now, no deal exists, no partial deal exists and unless Iran is able to make the difficult decisions that are required there won't be a deal," he said.