Europe to open lower ahead of Fed

European equities are expected to open lower on Tuesday following a rate decision from the Bank of Japan and the start of a two-day meeting of the Fed's monetary policy committee.

The London FTSE 100 index is called to open 15 points lower at 6,150, the German DAX down 17 points at 9,973 and the French CAC down 9 points at 4,498, according to IG.

European markets look set to follow a shaky lead in Asia where markets were mostly lower overnight. The Bank of Japan decided to keep its monetary policy steady rather than increasing its firepower. Economists now expect further stimulus in July as the central bank waits to assess the impact of its uncharted entry into negative interest rates.

Investors around the world have now turned their attention to a two-day meeting of the U.S.' Federal Open Market Committee (FOMC) which begins on Tuesday (with an interest rates decision due Wednesday). No move on rates is expected, but comments from policymakers will be scrutinized for indications on the path of tightening.

Later this week, the Bank of England meets on Thursday and Norway and Switzerland also hold central bank meetings.

Oil prices retreated during Asian hours, following a drop in prices overnight on renewed concerns about oversupply. U.S. crude futures were down 0.65 percent at $36.94 a barrel, following a decline of 3.4 percent during U.S. hours. Global benchmark Brent shed 0.78 percent to $39.22 a barrel, after finishing lower by 2 percent overnight.

In a surprise move on Monday, Russia President Vladimir Putin announced that "the main part" of Russian armed forces would start to withdraw from Syria. The news comes as U.N.-mediated peace talks aimed at ending the five-year-old civil war have resumed.