WASHINGTON ― President Obama is approaching one of those moments when a big turn in foreign policy is possible. People can debate whether it’s the equivalent of the opening to China or the end of the Cold War, but there’s no doubt that this is a time of opportunity ― and that, as the old English proverb put it, “there’s many a slip twixt cup and lip.” 

What was unthinkable only a few months ago with Iran and Syria now appears to be in motion. On Iran, Obama has talked directly with President Hassan Rouhani about quickly negotiating a deal to limit the Iranian nuclear program. On Syria, the U.S. and Russia have agreed on a U.N. plan to destroy President Bashar al-Assad’s stockpile of chemical weapons.

Because this diplomacy engages countries that have been our adversaries, some observers see signs of American weakness or even capitulation. They’re mistaken. America will be stronger if it can create a new framework for security in the Middle East that involves Iran and defuses the Sunni-Shiite sectarian conflict threatening the region. But change frightens people, especially when it’s being pushed by a president who is perceived as weak at home and abroad.

Tactical finesse matters in big strategic moments like this. That’s one lesson I take from the way President Richard Nixon (with Henry Kissinger) shaped the opening to China in the early 1970s and Presidents Ronald Reagan and George H.W. Bush (with Brent Scowcroft and James Baker) managed the end of the Cold War in the late 1980s. They made it look easy to alter policies and alignments that had been in place for generations.

One thing the Nixon and Reagan-Bush teams did well was manage communications: The opening to China was accompanied by regular dialogue with the Soviet Union, the nation most affected by the shift in U.S. policy. The later endgame with the Soviets required frequent contact with U.S. allies in Europe, who were frightened both by Reagan’s hawkish challenge to Moscow and Bush’s push to unify Germany. U.S. diplomats were on airplanes nearly every week to reassure allies.

To get around the corner with Iran, Obama will need a deal that verifies Supreme Leader Ali Khamenei’s pledge not to build a bomb ― and also prevents any quick breakout capability. Iran will have to cap its level of uranium enrichment (at, say, 5 percent) and also its stockpile of enriched material. These numbers must be low enough that Iran would need months to dash for a bomb ― long enough that the U.S. and Israel would have strategic warning. In exchange the West could accept Iran’s right, in principle, to enrich.

The elements of a workable Iran deal are obvious to all. What’s crucial is that, moving forward, the U.S. communicate frequently ― not just with its negotiating partners in the P5+1 group but also with neighboring countries such as Saudi Arabia, Bahrain, the United Arab Emirates and Turkey, as well as Israel. Indeed, Obama should invite regional leaders to Camp David this fall to explore new security structures for the Gulf.

Regional coordination may be even more important with Syria. The Saudis and Qataris are still pumping money into a Syrian opposition that’s dominated by jihadists. This is like filling a balloon with poison: Foreign fighters are rushing to Syria to join the well-financed jihad, including nearly 100 British Muslims, more than 130 French, more than 100 Australians, and as many as 800 Saudis. This is truly dangerous.

The path toward a more stable Syria passes through Geneva, with the negotiations for political transition being discussed now by the U.S. and Russia. If all parties (including Iran) can agree that Assad will not run again when his term concludes next year, the Syrian nightmare could begin to end. The moderate Syrian opposition needs to show that in this post-Assad Syria, it can help maintain state institutions. An American official needs to coordinate the overt and covert strands of policy and drive it toward Geneva. Leaving this delicate process to Saudi Arabia, Qatar and their checkbook jihad would be nuts.

Obama and Secretary of State John Kerry must communicate that America is reaching an inflection point: In the world that’s ahead, Iran must temper its revolutionary dreams of 1979, just as Saudi Arabia must stop hyperventilating about the “Shiite crescent.” What’s around the corner is a new regional framework that accommodates the security needs of Iranians, Saudis, Israelis, Russians and Americans.

It’s a truly big deal ― but it will require constant, skillful diplomatic guidance.

By David Ignatius

David Ignatius’ email address is davidignatius@washpost.com. ― Ed.

(Washington Post Writers Group)