KABUL, Afghanistan — Afghanistan this weekend joined Syria and Venezuela and became the newest member of a select club of nations: those that have publicly backed the Russian annexation of Crimea.

Citing “the free will of the Crimean people,” the office of President Hamid Karzai said, “we respect the decision the people of Crimea took through a recent referendum that considers Crimea as part of the Russian Federation.”

To the casual observer, becoming the first Western-backed democracy to express support for the widely denounced referendum in Crimea might seem an odd tack for Afghanistan, which is heavily dependent on assistance from the United States and European countries. Those nations wholeheartedly condemned the Russian takeover of Crimea, and were unlikely to be supportive of Mr. Karzai’s decision.

But Russia’s insistence that it is righting a historical wrong in retaking Crimea, which was ceded to Ukraine by Soviet authorities in 1954, resonates in Afghanistan. Here, many believe that the Pashtuns, the country’s largest ethnic group, were unjustly cut off from their brothers and sisters when Britain laid down a border to separate Afghanistan from imperial possessions in South Asia.