WASHINGTON - Criticized for his low-profile diplomacy, Secretary of State Rex Tillerson is emerging from the shadows with a leading public role in shaping and explaining the Trump administration's missile strikes in Syria. And, he's set for an even higher-profile mission, heading to Moscow under the twin clouds of Russia's U.S. election meddling and its possible support for a Syrian chemical weapons attack.

Since taking office in February, the former Exxon Mobil CEO has admittedly shunned the spotlight and the press. Yet, Tillerson was surprisingly visible during last week's announcement of the response to the gruesome chemical attack, fielding questions from reporters on and off camera, and then captured in an official White House photo seated next to U.S. President Donald Trump as they heard the result of the 59 cruise missiles that struck a Syrian military base.

Tillerson was a prominent fixture during the most important foreign policy period in Trump's young presidency: a two-day summit with Chinese President Xi Jinping that coincided with the strikes against Syria. He was by Trump's side during his meetings with Xi and spoke publicly multiple times to address both issues.

It was Tillerson who delivered the Trump administration's first blistering condemnation of Russia in the hours after the strikes. Standing in a cramped conference room alongside national security adviser H.R. McMaster, Tillerson said Moscow had "failed" to live up to its obligations under a 2013 agreement to strip Syria of its chemical weapons stockpiles. "Either Russia has been complicit or Russia has simply been incompetent in its ability to deliver on its end of that agreement," he said.

On Sunday, he made his first network television interview appearances. In one interview, Tillerson said he sees no reason for retaliation from Russia for the U.S. missile strikes. Russia maintains a close political and military alliance with President Bashar Assad's government and has been accused of supporting its attacks against Syrians opposed to Assad's rule - something Moscow adamantly denies.

Tillerson said on CBS' "Face the Nation" that Russians were not targeted by the strikes. He also said the top U.S. priority in the region hadn't changed and remained the defeat of Islamic State militants.

Then he headed to Europe to gather with the foreign ministers of the other major industrialized nations before venturing on eastward to become the first Trump Cabinet member to visit Moscow - and possibly meet with Russian President Vladimir Putin.

The criticism from the foreign policy establishment's left and right that has dogged Tillerson's tenure is dying down.

Tillerson had faced questions about whether he understood that his new position meant he was now the face of the United States to the world, that he had to answer no longer to a small group of top shareholders but to more than 320 million Americans.

The secretary of state must be "the spokesman for American foreign policy," said Eliot Cohen, a senior State Department official during George W. Bush's presidency. "This is the administration's first crisis but it won't be their last by a long shot, so he's going to have to get used to this."

Joining Trump at the president's Mar-a-Lago resort in Palm Beach, Florida, Tillerson was supposed to focus on the informal summit with Xi. Instead, he was thrust to the forefront after photos of the bodies piled in heaps in Idlib, Syria, dramatically altered the agenda.

Only a week earlier, Tillerson had alarmed U.S. allies by indicating the U.S. was no longer interested in pushing for Assad's removal from power.

In the hours leading up to Trump's decision to order the strikes, Tillerson was among the most forward-leaning of Trump's top aides in suggesting the U.S. would deliver an "appropriate response." He challenged Russia publicly in a way Trump appeared scrupulously to avoid and said of Assad early Thursday: "It would seem that there would be no role for him to govern the Syrian people."

After the cruise missiles crashed down in Syria, Tillerson was calm and commanding in a question-and-answer session with journalists.

Cohen, a conservative critic of Trump's foreign policy who has chided Tillerson for his reticence, said he saw Tillerson growing into the job. "I suspect you'll see more of him as he grows more comfortable in dealing with the press and in his relationship with the president and the administration's national security team," Cohen said.

The challenge will be greater in Russia's capital this week. Tillerson is arriving at a fragile point in U.S.-Russia relations, where he will have to confront the Kremlin's anger over the missile strikes in Syria along with suspicion at home that Moscow may have been complicit in the Syrian government's chemical weapons attack. Senior U.S. military officials have said they are looking into whether Russia provided drone surveillance and helped Syrian forces try to cover up what they'd done.

"I think that there will be a lot of answers that come out of that meeting. And I think that's when the president will make his decisions," said Nikki Haley, the U.S. ambassador to the United Nations, during an appearance on CNN's "State of the Union."

Beyond Syria are disputes over Russia's 2014 annexation of Ukraine's Crimea region and support for pro-Russian separatists in eastern Ukraine.

At the same time, Tillerson carries to Moscow the weight of FBI and congressional investigations into Russia's interference in last year's presidential election. The Trump campaign's possible ties to the presumed Russian meddlers are also under scrutiny.

"This is going to be Tillerson's biggest test to date," said Julianne Smith, a National Security Council and Defence Department official under President Barack Obama.

When he goes to Russia, keeping a low profile would likely be impossible, even if it were his goal.

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Associated Press writers Josh Lederman and Julie Pace contributed to this report.