Armed men, believed to be Russian servicemen, walk outside a Ukrainian military base in Perevalnoye, near the Crimean city of Simferopol, March 14, 2014. Vasily Fedosenko / Reuters The U.S. is not sharing with Ukraine information, analysis, and intercepts that signal a growing likelihood of a full-scale invasion by Russia, The Daily Beast reports, citing a senior U.S. intelligence official.

The intelligence, which could help Ukraine better position troops in an effort to defend its eastern cities, has reportedly been gathered by a network of American spies and intelligence officers.

There is a fear that by divulging American intelligence to Ukraine, Russia may learn of U.S. sources and methods.

Eli Lake, of The Daily Beast, reports:

In the case of Ukraine, the United States historically does not share much out of concern that the information provided to Kiev would make its way back to Moscow. Until February, Ukraine’s military maintained close ties to Russia. The chances that its military is penetrated by Russia’s military intelligence agency, the GRU are high.

So far, events in the east of Ukraine have followed a similar pattern as in Crimea. Pro-Russian separatists have built barricades and seized buildings in three cities and demanded a referendum for independence from Kiev.

U.S. Secretary of State John Kerry has accused Russian Special Forces of being behind the chaos. If this is the case, then Russia could already have put the wheels in motion for an offensive.

It is currently estimated that Russia has upwards of 80,000 troops on the Ukrainian border.