A year after the deadly attack on the U.S. mission in Benghazi, Libya, President Obama’s pledge to bring the perpetrators to justice has yet to be fulfilled.

The fact that leading suspects in the attack, which killed ambassador J. Christopher Stevens and three others, operate openly in Benghazi, occasionally offering interviews to U.S. media, is particularly galling.

Some wonder why the administration does not push the Libyan government harder to take action against the suspects or the Ansar al-Sharia militia, which joined the assault. Others say Obama should launch a unilateral U.S. raid, like that which killed Osama bin Laden.

In fact, there are good reasons for prudence. Setting aside the reality that Obama already has placed U.S. forces on alert for possible action in Syria, an American action in Libya could have a high political cost, even if it succeeded.

The Libyan government and much of the population views the United States favorably because of its help in overthrowing dictator Moammar Gadhafi; a strike could squander that rare goodwill in an Arab state.

could also further destabilize a moderate regime that already is struggling to keep the country’s economy functioning and complete the construction of a new democratic political system.

What Libya needs from Washington is not a special-forces raid but much more help in building a state. After helping to liberate Libya, the Obama administration and its European allies were too quick to walk away. If they wish to avoid another Arab state descending into chaos, they need to come back.