UPDATE 1-White House to China: World must reject Russian action on Ukraine

(Recasts with Kirby comment on China; adds quotes. Changes slug to UKRAINE-CRISIS/USA)

WASHINGTON, Sept 15 (Reuters) - The White House on Thursday urged China not to back Moscow in its war against Kyiv, saying the whole would should be aligned against Moscow's aggression in Ukraine and not remain on the sidelines.

"We don't think anybody should be on the sidelines," White House spokesman John Kirby told CNN in an interview on Thursday as Chinese President Xi Jinping met Russian President Vladimir Putin at a summit in Uzbekistan. "The whole world should be lined up against what Mr. Putin is doing."

"This is not the time for any kind of business as usual with Mr. Putin," Kirby added.

Xi and Putin were meeting on the sidelines of the Shanghai Cooperation Organisation summit in their first face-to-face meeting since Russian troops invaded Ukraine in February.

Kirby said it remained to be seen how much China would back Russia's war, noting that Beijing had not moved to materially support Putin or violated sanctions against Moscow.

Separately, Kirby told MSNBC that the United States is preparing to send Ukraine another package of security assistance but declined to give further details, including when the tranche would come.

The announcement was expected to come "very, very soon," he added on CNN. (Reporting by Susan Heavey Editing by Raissa Kasolowsky)