Oil markets are deeply concerned about the power President Donald Trump has over some of the world's largest crude producers, energy analysts told CNBC on Wednesday, ahead of a much-anticipated meeting between OPEC and non-OPEC members.

The influential oil cartel and its allied partners are gathering in Vienna, Austria, this week, with the aim of reaching an accord to deliver a fresh round of supply cuts.

But, even with the oil market near the bottom of its worst price plunge since the 2008 financial crisis, few external observers expect the energy alliance to engineer a succinct production quota that satisfies oil traders.

"This is the first time I think we have come into an OPEC meeting that is so political. We literally don't know how they are going to message this," Amrita Sen, chief oil analyst at Energy Aspects, told CNBC's Hadley Gamble in Vienna.

"Given how fragile the market is, the market's biggest fear is that it doesn't matter whether OPEC understands fundamentals, it is Trump that is controlling OPEC policy."

"And if they are unable to communicate what they are going to do very clearly — which I think there is a big risk that they can't — the market is going to sell-off because their biggest fears are going to get confirmed," Sen said.