WASHINGTON — Just days before Vladimir V. Putin reassumed the presidency of Russia last year, President Obama dispatched his national security adviser to Moscow. Mr. Obama had made considerable progress with Dmitri A. Medvedev, the caretaker president, and wanted to preserve the momentum.

Any hopes of that, however, were quickly dashed when Mr. Putin sat down with the visiting American adviser, Tom Donilon, at the lavish presidential residence outside Moscow. Rather than talk of cooperation, Mr. Putin opened the meeting with a sharp challenge underscoring his deep suspicion of American ambitions:

“When,” he asked pointedly, “are you going to start bombing Syria?”

At the time, Mr. Obama had no plans for military involvement in the civil war raging in the heart of the Middle East, but Mr. Putin did not believe that. In Mr. Putin’s view, the United States wanted only to meddle in places where it had no business, fomenting revolutions to install governments friendly to Washington.

The meeting 16 months ago set the stage for a tense new chapter in Russian-American relations, one that will play out publicly this week when Mr. Obama travels to St. Petersburg for a Group of 20 summit meeting hosted by Mr. Putin. Although Mr. Obama had no intention of bombing Syria last year, on Saturday he said he now favored military action against Syrian forces, not to depose the government of Bashar al-Assad, a Russian ally, but in retaliation for gassing its own citizens — an assertion Mr. Putin denounced as “utter nonsense” to justify American intervention.

While it was the Kremlin’s decision last month to shelter Edward J. Snowden, the National Security Agency leaker, that finally prompted Mr. Obama to call off a separate one-on-one meeting he had scheduled with Mr. Putin while in Russia, the core of the schism is not so much that case as the radically different worldviews revealed by the Syria dispute. Where Mr. Obama feels compelled to take action to curb the use of unconventional weapons, Mr. Putin sees American imperialism at work again.