A battle for control of the Libyan capital remained deadlocked for a fifth day on Tuesday, as the city’s last civilian airport resumed flights after an airstrike and the United Nations canceled a long-planned peace conference scheduled for later this month.

The airport reopened Tuesday after closing the day earlier, following an airstrike there by the forces of an aspiring strongman, Gen. Khalifa Hifter. But although it resumed flights, the United Nations mission canceled a conference set to take place in Libya.

The cancellation was almost universally expected since troops under General Hifter on Thursday launched a surprise offensive on the capital, Tripoli.

Ghassan Salame, the United Nation’s special representative for Libya, said in a statement that the body “cannot ask Libyans to attend a conference to the backdrop of artillery shelling and air raids.” He said it was “a painful disappointment to once again hear the drumbeats of war and to witness the launch of an offensive prompting the recurrence of fighting.”