As Russia’s foreign minister made clear that Moscow’s territorial ambitions extend beyond Ukraine’s eastern territories, the United States said on Wednesday it would send four more advanced multiple-missile launch vehicles to Ukraine. The rocket launchers, which can fire salvos that rival the devastating effects of an airstrike from a jet loaded with precision bombs, are part of a series of new, longer-range weapons the United States is providing the decimated Ukrainian military. They underscore Washington’s determination to help counter Russian military might and President Vladimir Putin’s goal of subduing Ukraine, a sovereign country. But with Russia until recently making gradual but steady gains on the battlefield and Ukraine’s Western allies struggling to keep up with Ukraine’s seemingly insatiable appetite for weapons, Ukraine faces an uphill battle to gain parity on the field of battle. And there are disagreements between Ukrainian and American officials about what that would require. Briefing reporters at the Pentagon on Wednesday, Defense Secretary Lloyd J. Austin III said the four more advanced multiple launch vehicles will bring the total number provided by the United States to 16. Video Defense Secretary Lloyd J. Austin III announced that the US military will send additional advanced missile systems to help Ukraine defend itself.CreditCredit…Alex Brandon/Associated Press Mykhailo Podolyak, an adviser to Ukrainian President Volodymyr Zelensky, said in June that Ukraine needed 300 multiple-launch missile systems and 500 tanks, among other things, to better compete with the forces Russia might have. This is several times more than what Ukraine has promised. Michael G. Vickers, the Pentagon’s former top civilian official for counterinsurgency strategy, said this month that the Ukrainians needed at least 60, and perhaps as many as 100, HIMARS or other multiple launch missile systems to win their battle artillery. Also looming over arms transfers is the question of how long American resolve will last amid high gasoline prices and increasing demands for national sacrifice in Europe and the United States. The Biden administration has also been reluctant to provide weapons that could reach Russian soil and potentially trigger a wider war. The dozen M142 HIMARS — an acronym for High Mobility Artillery Missile Systems — already provided by Pentagon stockpiles have already made a difference on the battlefield, Mr. Austin said. Ukrainian soldiers have used them to destroy Russian command and control centers and ammunition depots. Each M142 HIMARS truck carries six guided missiles packed with 200 pounds of high explosives that can strike targets 50 miles away. “That affects the pace of the race and potentially creates some opportunities here,” Mr Austin said. “There is still much to do – HIMARS alone will not change, win or lose a race.” Ukraine’s Defense Minister Oleksii Reznikov said this week that Ukraine’s military needed at least 100 of the US launchers to “change the game on the battlefield.” HIMARS and other missile launchers already deployed to Ukraine have helped destroy about 30 Russian command posts and ammunition storage units, he said. “This has significantly slowed the Russian advance and dramatically reduced the intensity of the artillery bombardment,” Mr Reznikov said in an online interview on Tuesday for the Atlantic Council, a Washington research group. “That’s how it works.” As debate continues in the West about what it takes to rein in Russian forces, Russian Foreign Minister Sergei V. Lavrov said Wednesday that Russia’s ambitions in Ukraine now extend beyond the country’s eastern territories, a departure from the Kremlin’s previous claims that it is not waging a war of imperial expansion. As Ukraine has stepped up attacks against Russian forces in southern Ukraine as a possible prelude to a large-scale counter-offensive, Mr Lavrov said Moscow was also monitoring the Kherson and Zaporizka regions in southern Ukraine, parts of which are held by the Russian forces, as well as “a number of other areas”. Eric Schmitt contributed reporting.