Why is Trump vacillating in supplying Ukraine with lethal defensive weaponry?

Recall that at 2017 BRICS Summit in Xiamen, Fujian province in China, September 4, 2017,

"Russian President Vladimir Putin said on Tuesday that any decision by the United States to supply defensive weapons to Ukraine would fuel the conflict in eastern Ukraine and possibly prompt pro-Russian separatists to expand their campaign there" (Denis Pinchuk : Reuters : September 5, 2017) (my emphasis)

This was a response of Putin to U.S. Defense Secretary Jim Mattis (right) who in Kiev, on Ukraine's Independence Day, stated that,

“On the defensive lethal weapons, we are actively reviewing it, I will go back now having seen the current situation and be able to inform the secretary of state and the president in very specific terms what I recommend for the direction ahead,” Mattis said.

“Defensive weapons are not provocative unless you are an aggressor and clearly Ukraine is not an aggressor since it is their own territory where the fighting is happening,” Mattis said" (Idrees Ali and Pavel Polityuk : Reuters : August 24, 2017) (my emphasis) 

And in three day's time, as Jonathan Marcus reports,

"It is being billed as a military exercise, but when Russian and Belarusian forces start Zapad-2017 this week, many neighbouring countries will be looking on nervously.

Zapad-2017 ("West-2017") is a joint strategic-level exercise involving Russian and Belarusian military forces, expected to begin on 14 September in Russia's western military district Kaliningrad, and across Belarus." (BBC News : 11 September, 2017) (my emphasis)

Ukraine's President, Petro Poroshenko, is in no doubt about the threat that Putin's Zapad-2017 so-called 'military exercises' poses for Ukraine.

"[..] President Petro Poroshenko says he fears that Russia could use massive military manoeuvres next week as a cover for invasion.

In a major speech, Mr Poroshenko said Russia's Zapad-2017 exercises with Belarus might be "a smokescreen to create new Russian army assault groups to invade Ukrainian territory". (BBC News : 7 September 2017) (my emphasis)

This possible Putin smokescreen "to create new Russian army assault groups to invade Ukrainian territory" would be aided by the fact that:

• Donald Trump and his White House staff are currently pre-occupied with the devastating effects that hurricane Irma is having on Florida, and
• Angela Merkel is currently caught up in the throes of the German Chancellorship elections.

Added to which, US Defence Secretary Jim Mattis simply recommended to Trump and Rex Tillerson, US Secretary of State, that the US should supply Ukraine with defensive lethal weapons.

This recommendation of Mattis to Trump and Tillerson (right: Tillerson & Trump) that the US supply Ukraine with lethal defensive weaponry happened towards the end of August, before hurricane Irma formed.

And whilst Trump has not yet signed off on supplying Ukraine with lethal defensive weaponry, NATO Chief General Jens Stoltenberg has,

"...  urged Moscow to meet its international commitments to be fully transparent about war games planned for next month in Belarus and western Russia. 

"We are going to be watching very closely the course of these exercises," Stoltenberg told journalists in Warsaw on August 25.." (RFERL : August 25, 2017) (my emphasis)

Which begs the question,

"Why is Donald Trump vacillating in giving the go-ahead to supply Ukraine with lethal defensive weaponry?"

(to be continued)