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(CNN) -- After more than a dozen trips to the Middle East and 14 months of unbridled optimism on the prospects for peace in the region and his own ability to negotiate it, John Kerry on Friday finally sounded defeated. While Kerry has made the peace process his priority since taking office, his focus has been challenged by the civil war in Syria, nuclear negotiations with Iran and, now, Russian moves against Ukraine. He acknowledged the Israeli-Palestinian conflict was still a global concern, but that the United States had a full agenda. "We have an enormous amount on the plate," he said, adding what were possibly the toughest comments he has made about the parties' intransigence. "There are limits to the amount of time and effort that the United States can spend if the parties themselves are unwilling to take constructive steps in order to be able to move forward," Kerry said. The past week was particularly frustrating for Kerry. Israel reneged on a scheduled release of Palestinian prisoners and the Palestinians responded by signing on to join 15 international bodies in defiance of their own commitment not to seek international recognition as a state. Kerry blindly stated the obvious when he called both moves "not helpful." Since beginning his peace mission, Kerry's lofty goals have become significantly more modest. In July, he announced a bid to reach a peace deal within nine months. But as time rolled by with little progress, Kerry sought to get Israeli Prime Minister Benjamin Netanyahu and Palestinian President Mahmoud Abbas to agree to a framework, which would form the basis for a comprehensive peace treaty. With the deadline set to expire on April 29, Kerry and his aides have struggled to get the parties to extend the talks, even putting the potential release of Israeli spy Jonathan Pollard on the table to secure the Palestinian prisoner release. Kerry said "neither party has said that they've called it off." And one Palestinian source close to the negotiations told CNN's Ben Wedeman that Palestinians were still committed to the talks until the April deadline. After that, he said, "we are free." Neither of those are ringing endorsements. Even if both sides are willing to mark time for another month, it's clear the peace process is on life support. While Kerry isn't ready to pull the plug entirely, he said the United States would "evaluate what is possible and what is not possible," suggesting Washington may recalibrate its role as broker of the peace process as a result. "We're not going to sit there indefinitely. This is not an open-ended effort," Kerry said Friday in Morocco. "It's reality check time."

Kerry had high hopes of deal in announcing talks nine months ago .
He has made more than a dozen trips to the region to facilitate negotiations .
He had been optimistic, but now he sounds resigned with deadline for progress fast approaching .
Kerry says the U.S. will now evaluate what's "possible and what is not possible"