Janet Yellen
US Federal Reserve Chair Janet Yellen speaking in Washington in 2015.Reuters

US equities turned sharply south today (27 January 2016) amid a renewed decline in oil prices, while investors remained jittery ahead of the conclusion of a two-day Federal Reserve meeting. Shortly before the opening bell, the Dow Jones Industrial Average was down 0.70% to 16,053.96, while the S&P 500 and Nasdaq were 0.30% and 0.49% lower respectively.

The latest policy decision from the US central bank, which is set to be announced at 2pm EST (7pm GMT), is to be closely followed by market participants, as it will be the first time since raising interest rates in December 2015 that the Fed will offer a hindsight on its stance. The global economic picture has changed over the last month and a half, and some have suggested the US central bank might have tightened its monetary policy too soon.

"One key to global financial stability is a weaker US dollar. We'll get a sense of whether the Fed 'gets it' today [27 January]," said Jack McIntyre, portfolio manager at Brandywine Global Investment Management.

"I do not think that the Fed will reverse course in 2016 and start cutting rates, but they need to start sounding more dovish, at least on the margins," he added.

"They need to tell investors they are going to focus more on inflation because that gives them the cover to tighten at an extremely slow pace going forward."

Oil prices slid again after the American Petroleum Institute said yesterday that crude supplies climbed by 11.4m barrels last week, while the US Energy Information Administration is reporting later in the session.

Brent crude fell 0.35% to $31.69 (£22.11, €29.08) a barrel while West Texas Intermediate fell 1.62% to $30.95 a barrel. Elsewhere, Asian stocks closed mixed, with the Shanghai Composite Index closing 0.52% down and the Nikkei's 225 rising 2.72% while European stocks were broadly flat – although midway through the afternoon, London's FTSE 100 managed to gain 0.3%.

On the company front, Apple was firmly in the red after revealing late in the previous session that iPhone sales in the fourth quarter grew at the slowest pace since it was introduced in 2007.

"Warnings about slowing iPhone sales reminded markets that, for all its innovations, the firm is still essentially dependant on its iconic smartphone for its daily bread," said Chris Beauchamp, senior market analyst at IG. "If this falters, no amount of modest growth in iPad or Watch sales will help."

Boeing plunged after the aircraft producer delivered annual guidance for 2016 that was below analysts' forecast, while social-media heavyweight Facebook, eBay and telecom equipment-maker Qualcomm are to report after the close.