WASHINGTON — Concerned by the attempts of Al Qaeda and its global affiliates to attract more Americans and other Westerners, the State Department is stepping up its online efforts to combat violent extremists’ recruiting of English speakers.

The campaign is starting at a time when intelligence officials say dozens of Americans have traveled or tried to travel to Syria since 2011 to fight with the rebels against the government of President Bashar al-Assad. Al Qaeda’s branch in Yemen now puts English subtitles on its website propaganda. The Shabab, the Islamist extremist group in Somalia, publish an English-language online magazine.

State Department officials acknowledge that the new program is a modest trial run that faces a vast array of English-language websites, Twitter feeds, YouTube videos and Facebook pages that violent extremist groups have established largely uncontested in the past few years. But American and European intelligence officials warn that Al Qaeda’s efforts to recruit English-speaking fighters could create new terrorist threats when the battle-hardened militants return home.

For the past three years, a small band of online analysts and bloggers in a tiny State Department office have focused their efforts on trying to understand what inspires their target audience — men 18 to 30 years old, mostly in the Middle East — to violent extremism, and on finding ways to steer them away from that. The analysts speak Arabic, Urdu, Somali and Punjabi.