Stock index futures pointed to a lower start on Tuesday as Wall Street reopens following a long weekend, with investors rattled by mounting tensions surrounding North Korea.

At 4:05 a.m. EDT, futures for the S&P 500 were down 0.3 percent, Dow Jones futures were down 0.1 percent and Nasdaq 100 futures were down 0.6 percent.

European equities dropped 1 percent in early trade on Tuesday, with political risk at the forefront of investor concerns as North Korea, defiant in the face of international condemnation of its latest nuclear test, fired two short-range missiles off its east coast on Tuesday and accused the United States of plotting against its government.

In a move certain to compound tensions in the region, South Korea said it would join a U.S.-led initiative to intercept ships suspected of carrying weapons of mass destruction, something Pyongyang has warned it would consider a declaration of war.

Energy shares will be in focus as oil fell below $61 a barrel on Tuesday, dragged down by a recovery in the U.S. dollar and expectations that an OPEC meeting later this week would keep the cartel's output unchanged.

Investors will also keep a close eye on the fixed income front. The benchmark U.S. Treasury debt price rose in Asian trade on Tuesday, with the yield edging away from last week's six-month peak, while the market braced for $101 billion worth of government debt sales this week.

The U.S. Treasury sells $40 billion of two-year notes on Tuesday, $35 billion of five-year debt on Wednesday and $26 billion of seven-year paper on Thursday, matching a record for weekly bond sales set in April.

On the macro front, investors were bracing for key U.S. consumer confidence data for May, due at 10:00 a.m. EDT.

U.S. stocks retreated for a fourth session on Friday on persistent concerns over the U.S. budget deficit, with U.S. Treasuries and the dollar losing ground.

The Dow Jones industrial average <.DJI> dropped 14.81 points, or 0.18 percent, to 8,277.32. The Standard & Poor's 500 Index <.SPX> fell 1.33 points, or 0.15 percent, to 887.00. The Nasdaq Composite Index <.IXIC> lost 3.24 points, or 0.19 percent, to 1,692.01.

For the week, though, stocks finished moderately higher, with the blue-chip Dow average up 0.1 percent, the S&P 500 up 0.5 percent and the Nasdaq up 0.7 percent.

Since reaching a low in early March, the Dow has gained 28 percent and the S&P 500 has risen 33 percent.

Amgen Inc is exercising an option to acquire the rights to Cytokinetics Inc's experimental heart drug, the New York Times said on Tuesday.

(Reporting by Blaise Robinson; editing by John Stonestreet)

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