The House Foreign Affairs Committee voted narrowly on Thursday to condemn as genocide the mass killings of Armenians early in the last century, defying a last-minute plea from the Obama administration to forgo a vote that seemed sure to offend Turkey and jeopardize delicate efforts at Turkish-Armenian reconciliation.

The vote on the nonbinding resolution, a perennial point of friction addressing a dark, century-old chapter of Turkish history, was 23 to 22. A similar resolution passed by a slightly wider margin in 2007 [....].