Members of the U.N. hold a moment of silence for the 298 victims killed on Malaysian Airlines flight MH17.

The U.S. Ambassador to the U.N. becomes emotional as she offers condolences.

SOUNDBITE: SAMANTHA POWER, U.S. AMBASSADOR TO THE UN, SAYING:

"As we stared at the passenger list yesterday, we saw next to three of the passengers names the capital I. As we now know, the letter I stands for infant. To the families and friends of the victims it is impossible to find words to express our condolences."

Samantha Power told the U.N. Security Council the U.S. believes Ukrainian separatists backed by Russia brought down the plane using a surface-to-air missile.

SOUNDBITE: SAMANTHA POWER, U.S. AMBASSADOR TO THE UN, SAYING:

"Because of the technical complexity of the SA11, it is unlikely that the separatists could effectively operate the system without assistance from knowledgeable personnel. Thus, we cannot rule out technical assistance from Russian personnel