U.S. stocks have given up some of their gains and ended lower ahead of Monday meeting of the euro zone leaders. This meeting should produce a decision on Greece's debt crisis and remove uncertainty, which weighs on markets.

The Dow Jones industrial average dropped 99.89 points, or 0.55%, to 18,015.95. The Standard & Poor's 500 fell by 11.25 points, or 0.53%, to 2,109.99. The Nasdaq Composite retreated by 15.95 points, or 0.31%, to close at 5,117.

Asian stocks have started this week with cautious optimism. Hong Kong Hang Seng rose by 0.40%, or 107.37 points, to 26,867.90. Meanwhile the Nikkei rose by 0.99%, or 199.03 points, to 20,373.27. China mainland markets are on holiday today.

Hopes for a Greek deal were the key positive contributor ahead of today's meeting as a deadline for a 1.6 billion euro ($1.81 billion) payment to the International Monetary Fund expires on June the 30th.