Secretary of State John Kerry appeared on multiple political talk shows on Sunday to make the administration's case on the conflict in Ukraine. The downing of Malaysia Airlines Flight 17, he said on "Fox News Sunday," was a "moment of truth" for Russia in which Russian President Vladimir Putin needed to "exert all of the influences they have" to protect the integrity of an investigation into what happened.

Kerry's appearances were largely predicated on presenting the evidence that the United States already feels exists. He outlined his case to CBS's Bob Schieffer. Some Russians "are leaders of the separatists," he said, and "trained the separatists, support the separatists, and have to date not publicly called on the separatists to stand down or to be part of the solution." The attack involved an SA-11 missile, he said, adding that separatists "had an SA-11 right in the vicinity hours before the shoot."

To CNN's Candy Crowley, he said that "it's pretty clear that this is a system that was transferred from Russia into the hands of separatists." The United States detected a missile launch at the time of the crash from separatist territory, he said, and in the wake of the incident, a separatist leader was "bragging on the social media about shooting down a transport plane. And then when people learned it was a civilian aircraft, [they] pulled that off of the social media." He claimed that the United States also has "video showing a launcher moving back through a particular area there, out into Russia, with at least one missing missile on it."

But this evidence, he argued, wasn't enough. That's in part because the crash scene had been compromised, with "drunken separatist soldiers piling bodies into trucks," as Kerry described it to "Fox News Sunday" host Chris Wallace.

"We need an investigation, not the secretary of state just listing things that we do know, but a further investigation with international investigators with their trained personnel," Kerry told Schieffer, "with the people who can put all of the evidence together and draw the appropriate conclusions so that we don't have a he-said-she-said finger-pointing back and forth."

Wallace challenged Kerry on the Obama administration's reaction to the attack, questioning the effectiveness of existing sanctions. "What we are doing now," Kerry responded, "is trying to bring our European counterparts along. ... Four percent of Russia's trade is with the United States. Fifty percent of their engagement is with Europe. So we're trying to encourage our European friends to realize this is a wake-up call, and hopefully they will also join us in these tougher sanctions."

Kerry told Crowley that he'd been in contact with his Russian counterpart. "Yesterday, I had a discussion with Foreign Minister [Sergei] Lavrov," he said. "It was a direct and tough conversation. We'll see if anything happens as a result of that."

On ABC's "This Week," Kerry told host George Stephanopoulos exactly what he felt Russia should do. "President Putin should publicly call on the separatists -- he should engage in public support for the cease-fire," Kerry said. "He should engage with the separatists directly in order to release the hostages they have taken. He should encourage them immediately to engage in a political process that could bring peace to the region."