Ukrainian Troops Have Slowed Russian Advance

LONDON — A Western official says Ukrainian resistance has slowed Russia’s advance almost to a halt, and Ukraine has repulsed Russia’s attempts to take the strategic southern port of Mariupol despite weeks of bombardment.

But the official said Russian troops have not been pushed back from established positions, and had the capability to keep up a grinding war of attrition for some time — making a rapid breakthrough in negotiations aimed at ending the violence unlikely.

The official, who spoke on condition of anonymity to discuss intelligence matters, said Odesa, another strategic port on the Black Sea, was a key objective for Russia but there are no indications of an imminent siege.

Odesa has been spared major attack, though Russia has ships operating off the Black Sea coast. The U.S. also says Russia has increased naval activity in the northern Black Sea, but there are no indications at this point of an imminent amphibious assault on Odesa.