President Obama’s negotiated nuclear agreement with Iran is encountering skepticism, even within his own Democratic Party. Republicans say they’ll reject the deal. That will take a congressional joint resolution. Obama says he’ll veto it.

It was a different scenario but the same cast of characters more than 40 years ago, beginning with a chain of events that came to be known as “ping-pong diplomacy.”

Nagoya, Japan, hosting the 1971 World Table Tennis Championship. After one particular practice, American player Glenn Cowan missed the team bus back to the team’s living quarters. The team from the People’s Republic of China waved Cowan aboard their bus.

Ten minutes into the 15-minute trip, Zhuan Zedong, China’s star player, left his seat and greeted Cowan. In that era it was a daring gesture.

“The trip on the bus took 15 minutes, and I hesitated for 10,” Zhuan said in a 2002 interview. “I grew up with the slogan ‘Down with American imperialism!’ And during the Cultural Revolution (1966-76), the string of class struggle was tightened unprecedentedly, and I was asking myself, ‘Is it OK to have anything to do with your No. 1 enemy?’”

That Zhuan and Cowan exchanged small gifts and sparked a friendship that evolved into exhibition matches in both countries and a state visit to China by then-President Richard Nixon. The table tennis players were among the first Americans to visit China since the Communist takeover of 1949.

Although Americans today remain wary, China is our country’s greatest trading partner. It can be argued that a steady U.S. export of free-market principles over 45 years has permanently altered the business climate, standard of living and diplomatic outlook in China.

It was Iran that shattered America’s exuberant decade of the 1970s. The decade when Americans celebrated moonwalks, completion of the World Trade Center, a patriotic bicentennial and, yes, even international table tennis ended badly when 52 American diplomats and other embassy workers were taken hostage for 444 days by a mob of Iranian college students.

We still call it the Iran hostage crisis. Iranians call it the “Conquest of the American Spy Den.” And the students who overthrew the Shah’s reign, overran the American embassy in Tehran and took American hostages are now the leaders of a rogue nation.

But Iran has grown tired of being the rogue. Economic sanctions have taken their toll. The defiant rhetoric masks the Persian people’s desire to join the modern world and enjoy the fruits of an open market.

Naturally, Americans old enough to remember the hostage crisis are wary of the deal — or of any deal with Iran. Like the Chinese table tennis players, two generations of Iranian people have grown up under the slogan “death to America.”

The distrust is deeply ingrained — just as it was in 1971 when a wary ping-pong player hitched a ride on Team China’s bus.

Now is the time for 45 years of ping-pong diplomacy to pay a dividend. China has not been an exemplary model a rogue nation in transition to democratic principles. The Communist Party, which remains in firm control, has been criticized frequently for human rights violations.

However, China has warmed steadily and considerably over the past four decades.

China can serve as an example to Iran of what’s possible if Iran gets on track as a responsible citizen of the world. China also should remind Americans that the diplomatic route can take time and a lot of work.

Maybe the negotiated nuclear arms deal with Iran didn’t happen as casually as an accidental bus ride. Bit it might lead to a similar destination.