BAGHDAD — Iraq’s security forces, which suffered huge casualties in the nine-month-long slog to take back the city of Mosul, are replenished enough to begin the fight for the Islamic State stronghold of Tal Afar — one of the last urban areas held in Iraq by the militant extremist Sunni group, American defense officials said Friday.

But the estimated 1,000 Islamic State fighters who are believed to be there could make a brutal and bloody last stand, the officials said, because Tal Afar has been encircled by Iraqi and Kurdish forces, making it difficult for the fighters to flee in large numbers.

In Mosul, Iraqi soldiers “took severe casualties” in the battle to retake the city, which began in October and did not end until July, said Gen. Joseph L. Votel, the head of United States Central Command. But, he added, “I think they are ready,” one month after hostilities ended there, to launch the next big fight.

His comments came during a press briefing with reporters aboard his flight Friday from Baghdad to Islamabad, Pakistan, where he is meeting with Pakistani leaders.