On Saturday, an explosion badly damaged the Kerch Strait Bridge linking Russia to Crimea, a symbol of Mr. Putin’s seizure of that peninsula in 2014 and a major supply route for his forces in southern Ukraine. Speaking on the condition of anonymity because the government is not publicly addressing the matter, a senior Ukrainian official confirmed that, as the Kremlin had charged, Ukrainian intelligence was responsible.
Russia’s domestic intelligence agency, the Federal Security Service, known by its Russian acronym F.S.B., said on Wednesday that it had arrested eight people, including five Russians, in connection with the explosion, which it said had resulted from a truck bomb.
In apparent retaliation for the bridge explosion, Russia stepped up attacks on cities in Ukraine to the highest level since early in the war, striking infrastructure like water and power systems, as well as homes. Ukraine says it shot down many of the cruise missiles and drones launched by Russian forces, but others got through, with deadly results.
When the war began, many military analysts thought that Russian air power would wipe out Ukraine’s air defenses in a matter of days or weeks, giving Moscow unchallenged control of the skies. That has not happened, and as a result, Russian warplanes rarely venture deep into Ukraine, where they risk being shot down.
General Milley and Mr. Austin acknowledged Ukraine’s need for still more air defenses, but did not say whether the United States had committed to sending specific systems that were not previously announced.
White House officials said on Tuesday that the Biden administration was working to deliver to Ukraine, as quickly as possible, two air-defense systems known as NASAMs, with a range of up to 30 miles. Such weapons are used to defend the White House and other sites in Washington from an aerial attack.
