President Obama has set a constructive new tone for trying to engage Iran.

President Bush’s failed policies have left Iran with enormous regional influence and frighteningly close to mastering the skills needed to build a nuclear weapon. The new administration will have to deal with Iran in a broader context, not just on the nuclear issue but also on Afghanistan and Iraq.

We don’t know if there is any mixture of incentives or sanctions that can wean Iran of its nuclear ambitions. But we are certain that the Bush administration never tried to find it. This means not only direct talks, but also far more persuasive incentives, including a credible offer of improved relations and security guarantees. Cooperation with Britain, France and Germany remains essential? and a much stronger push to try to bring the Russians and Chinese along.

We are not going to minimize the difficulties. Iran’s scientists are working aggressively to master nuclear fuel production, the hardest part of building a weapon. They just put a satellite in orbit, a sign that their ballistic missile program is moving ahead. It is difficult to read the politics in Tehran, but we are certain that hard-liners will try to sabotage any opening that would require making concessions on either program.

There will also be strong voices in Washington arguing against any compromise and some even for military action? a disastrous course. Iran’s support for Hamas and Hezbollah, its threats against Israel and its abysmal treatment of its citizens will only amplify those voices.

But we have seen the results of the Bush administration’s refusal to engage. It is time to at least test Tehran’s intentions.

That may be easier if the agenda for talks is broadened to include Afghanistan and Iraq. In 1998, Iran’s fundamentalist Shiiteled government nearly went to war with Afghanistan’s Sunni fundamentalist Taliban. After the United States ousted the Taliban in 2001, Tehran played a constructive role, helping establish a new government in Afghanistan. That limited collaboration quickly soured, and Iran has been accused of providing some support for the Taliban in an attempt to keep the Americans off balance. Mr.Obama needs to remind Iran that it is in its clear interest for the Taliban to be defeated and Afghanistan stabilized.

Iran’s relationship with Iraq is much more complicated. Analysts debate how much control Iran is seeking there and how much effort it is making to constrain extremists. But like the United States, Iran cannot possibly want Saudi Arabia, Turkey and other neighbors grabbing for pieces of Iraq when American troops leave. Mr.Obama can make a compelling argument that it is in Iran’s interest to join negotiations intended to guarantee Iraq’s longterm stability and sovereignty.

Mr.Obama is not presuming Tehran’s good will. Aides say he persuaded the Treasury Department’s Stuart Levey, who looked for creative ways to implement Mr.Bush’s sanctions policy, to stay on.

All that and more will be needed to try to make this work.