BRUSSELS — President Vladimir V. Putin of Russia has for years trumpeted grand ambitions for Moscow’s relations with the European Union, pushing to break down visa barriers and urging the creation of what he calls a “harmonious economic community stretching from Lisbon to Vladivostok.”

On a visit to the Brussels headquarters of the 28-nation bloc on Tuesday, however, Mr. Putin did not even get dinner. That customary courtesy was pulled from a sharply curtailed program — a small sign of the way escalating tensions over Ukraine have scrambled even basic rituals of diplomacy, chilled relations between Moscow and Brussels, and taken some of the shine off Mr. Putin’s image as a leader who can turn any crisis, even the mayhem in Syria, to his advantage.

As the European Union hosted the Russian leader for an “E.U.-Russia Summit” that lasted just three hours instead of the usual two days, the pillar of the Kremlin’s policy toward Ukraine, President Viktor F. Yanukovych, looked increasingly wobbly in the face of unrest that has spread to Russian-speaking areas previously rock solid in their support of him and his pro-Moscow tilt.

Early Tuesday, Mykola Azarov, the prime minister and a staunch ally of Mr. Yanukovych, resigned hours before the Parliament was due to hold a no-confidence vote that appeared likely to strip him of his powers. His departure was the latest sign of building momentum for the opposition, which first took to the streets in November after Mr. Yanukovych, under heavy pressure from Moscow, abruptly spurned a sweeping trade and political deal with the European Union.