Faced with a stream of conciliatory rhetoric from Iran's president, Hassan Rouhani, and a diplomatic overture to Tehran by Washington, Israeli officials are voicing scepticism and concern about a possible easing of western pressure on Iran to halt its nuclear programme.

The Israeli prime minister, Binyamin Netanyahu, says he will make Iran the focus of a meeting next week with the US president, Barack Obama, and a speech the next day at the UN general assembly, where he drew a red line on a cartoon bomb last year.

A statement from Netanyahu's office described the newly elected president's remarks about the peaceful aims of Iran's nuclear programme and his readiness to pursue diplomacy as an exercise in media spin. "The true test is not Rouhani's words, but rather the deeds of the Iranian regime, which continues to aggressively advance its nuclear programme while Rouhani is giving interviews," said the response, issued on Thursday after an interview the Iranian president granted to the American network NBC.

The statement raised the prospect of a reheating of old disagreements with the Obama administration over the handling of Iran, fuelled by an exchange of letters between Obama and Rouhani and talk in Washington of negotiations that could remove sanctions. Reflecting the Israeli government's concern that the US and Europe may be wavering, Netanyahu told a meeting of his cabinet last week that "the pressure on Iran must be increased and not relaxed, and certainly not eased".

Netanyahu asserted that Iran must halt all uranium enrichment, remove enriched uranium from the country, dismantle the Fordo nuclear plant and stop "the plutonium track" to a nuclear weapon.

Dore Gold, president of the Jerusalem Center for Public Affairs and a former adviser to Netanyahu, said: "Right now Rouhani is in the midst of a charm offensive, and there are officials all across the west who feel compelled to respond with hopeful signals about Iranian intentions.

"Israel is obviously focused on what actions Iran has taken. The real question is what tangible change you see in Iranian behaviour. We're not talking about mood music."

Other analysts were similarly sceptical. Rouhani "is really focused on the economic hardship in Iran as a result of sanctions, and that's why he wants to talk to the US and the international community," said Emily Landau, director of the arms control programme at the Institute for National Security Studies at Tel Aviv University. "He wants to get the sanctions off his back. He has given absolutely no indication that Iran is willing to reverse course on the nuclear issue."

Israeli officials are concerned that in return for an easing of sanctions, Iran could give up part of its nuclear programme while maintaining components that will enable it to move quickly towards building a bomb when it sees fit. Pointing to the recent confrontation with Syria over its alleged use of chemical weapons, the officials argue that a credible military threat has to be maintained to press Iran to change course.

Even as he pursues diplomacy with Iran, Obama has said the military option remains on the table.

But Yuval Steinitz, Israel's minister for strategic affairs, asserted in an interview published on Friday that such a promise was not enough. Claiming that Iran was six months away from developing a bomb, Steinitz told the right-leaning newspaper Yisrael Hayom that time had run out for negotiations.

Zalman Shoval, a former ambassador to the US and a special envoy for Netanyahu, said that while "officially there's no space between us and the Americans, we're more cautious, or perhaps more suspicious".

He added: "With the economic situation in Iran approaching bankruptcy in many respects, if the pressure is working it shouldn't let up at this crucial point."