Russian President Vladimir Putin forged an alliance with a terrorist organization in their efforts to defend Syrian President Bashar Assad, Secretary of State Rex Tillerson said Tuesday.

"Russia has really aligned itself with the Assad regime, the Iranians, and Hezbollah," Tillerson told reporters at the G-7 Summit in Italy. "Is that a long-term alliance that serves Russia's interest, or would Russia prefer to realign with the United States, with other Western countries and Middle East countries who are seeking to resolve the Syrian crisis?"

Putin has cultivated the image of a relentless opponent of terrorism since the first year of his rise to power, when he launched a war against Islamists in the Russian-controlled region of Chechnya. Tillerson's emphasis that Russia has an "alliance" with Hezbollah, a Lebanon-based Shiite Muslim terrorist group that is fighting on behalf of Assad in Syria and has warred with Israel, attacks that image on the eve of a trip to Moscow that Russia had hoped would lead to foreign policy concessions from the United States.

Tillerson criticized Russia for failing to destroy all of Assad's chemical weapons stockpiles, as they were obligated to do under a 2013 agreement negotiated with the Assad regime. "It is unclear whether Russia failed to take this obligation seriously or Russia has been incompetent, but this distinction doesn't much matter to the dead," he said. "We can't let this happen again."

President Trump talked repeatedly of working with Russia to defeat the Islamic State in Syria, but his decision to retaliate against Assad's use of chemical weapons that were deployed from an airbase that housed Russian forces working with the regime suggests that cooperation remains unlikely. Russian officials have responded angrily, announcing that Putin will not meet with Tillerson this week and promising to defend Assad from future U.S. attacks.

"From now on we will respond with force to any aggressor or any breach of red lines from whoever it is and America knows our ability to respond well," the Russian government said in a joint statement with Iran.

Putin cooperated with the United States in Afghanistan during former President Barack Obama's first term, but then-Secretary of State Hillary Clinton's condemnation of the corrupt 2011 elections in Russia evaporated any remaining good will from the "reset" of 2009. Then Russia annexed Crimea and backed a violent separatist movement in eastern Ukraine in 2014, which prompted the Obama administration and the European Union to hit Russia with aggressive economic sanctions.

"At the initiative of the former Washington authorities, Russia-U.S. relations plunged into deep crisis in recent years," the Russian Foreign Ministry said in a preview of Tillerson's visit. "We have a positive view of the willingness expressed by the new U.S. leadership to improve the situation, but we are proceeding based on the idea that actions speak louder than words."

Tillerson, who was criticized during his confirmation hearings for accepting an Order of Friendship award from Putin as CEO of Exxon Mobil, issued the rebuke over Russia's ties to Hezbollah from a meeting of the Western powers that imposed the sanctions.

"We want to relieve the suffering of the Syrian people," Tillerson said. "We want to create a future for Syria that is stable and secure. And so Russia can be a part of that future and play an important role, or Russia can maintain its alliance with this group, which we believe is not going to serve Russia's interest longer-term. But only Russia can answer that question."