Story highlights Secretary of State John Kerry and Russian counterpart Sergey Lavrov will meet in Moscow this week

The pair are expected to discuss the first US-Russian agreement to share intelligence about Syria

Washington, DC (CNN) When Secretary of State John Kerry meets with Russian counterpart Sergey Lavrov in Moscow this week, the big loser may be the man who isn't there: Defense Secretary Ash Carter.

Kerry and Lavrov are expected to discuss in detail the possibility of the first U.S.-Russian agreement to share intelligence and targeting data for airstrikes over the battle in Syria, something Carter has largely opposed.

The Pentagon wants some assurances the Russians will live up to the terms of any agreement in which the U.S. makes concessions. Defense officials told CNN that, internally, Carter has expressed skepticism the Russians can be trusted.

State Department spokesman John Kirby on Monday would not publicly acknowledge Kerry and Lavrov are discussing a potential agreement, saying only, "Syria will be front and center; there's no question about that."

He added, "I can assure you that one of the key topics the secretary is going to want to cover with Russian officials is reduction in violence."

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