BAMAKO, Mali — Islamist insurgents seized control of a village about 215 miles north of Bamako, Mali’s capital, on Monday, but the seeming setback in a 4-day-old French offensive to halt the advance of al-Qaida-linked rebels was seen as unlikely to slow plans for an expanded campaign to expel the rebels from the country’s north.

What provoked the rebel move on Diabaly, which one former resident described as home to fewer than 1,000 people, was unclear. Malian officials said that the militants, fleeing French airstrikes, weren’t trying to move closer to the capital but had targeted the village in their search for an escape route to nearby Mauritania.

But the loss of the Malian garrison at Diabaly highlighted the challenge facing France in its efforts to roll back the Islamists in a country as vast as Mali with a government as weak as the Malian one – a combination likely to allow rebels expelled from one area to pop up days later in some other corner of the country, crisscrossing on desert back roads.

In Washington, State Department spokeswoman Victoria Nuland said the United States would soon dispatch military trainers to nearby countries to train soldiers from other nations to take part in efforts to retake Mali’s north from the Islamists. Nuland said the Islamist rebels’ push south last week was “a wakeup call” that previous preparations to counter the Islamist seizure of two-thirds of Mali were “too leisurely.” The force hadn’t been expected to deploy until September.

So far the French, who began arriving in Mali late Thursday in response to a plea for help from Mali’s government, have relied on heavy airpower to pummel known rebel positions, even as French special forces operate missions from their base at the central Malian town of Sevare.

On Sunday, French planes hit rebel targets in the north’s largest city, Gao. But the city was quiet on Monday and there were no reports of bombing.

Four French planes were reported to have flown reconnaissance missions over the historic city of Timbuktu, now a headquarters for al-Qaida in the Islamic Maghreb. But they, too, did not attack rebel positions, though their presence did send rebels scattering.

The assault on Diabaly began when a rebel convoy of roughly 30 trucks that had camped overnight outside the village crossed a small lake Monday morning and engaged the Malian troops stationed there. The fighting lasted until around noon, when the government troops pulled out, according to a resident.

“There was some resistance. Then the military retreated, and rebels occupied the school and military camp. Only two of their pickups stayed behind, the rest of the rebel group continued on,” said Abdoulaye Ouologuem, a farmer in Diabaly who was interviewed by phone.

Some reports said that the battle represented a major rebel counterstrike, but people familiar with the village suggested those reports were overblown. One former resident said the town’s population is made up primarily of rice farmers who cultivate the swampy government-owned fields. The military outpost the rebels overran was used to stop illegal rice smuggling to Mauritania.

Government officials speculated that the rebel force had fled airstrikes against their positions in the towns of Konna and Lere and were searching for an escape route through the desert.

“They are panicked, and they want to run to Mauritania,” said Capt. Modibo Traore, a spokesman for the Malian military. He said the rebels had been pushed back to Diabaly after their passage was blocked by troops in the larger town of Sakolo a few miles away.