U.S. stock futures were mixed early Tuesday morning as investors return from a three-day weekend to a shortened week full of economic data. Oil prices have also kept their high levels due to ongoing supply concerns.

On the latest trading day, Friday, U.S. stocks once again finished the day with heavy losses -- it was the third time in four sessions. Reasons for the considerable declines included the continued climb of oil prices, inflation and economic concerns. Both General Motors (NYSE: GM) and General Electric (NYSE: GE) hit multi-year lows Friday. The Dow industrials ended Friday 145 points lower, or 1.16%, the S&P 500 fell 18 points, or 1.32%, and the Nasdaq Composite fell 19 points, or 0.81%. For the week, all three indexes lost some 3% to 4%.

On Friday, investors' mood was dampened by reading from the housing sector, as a report showed considerable inventory and the the number of unsold U.S. homes piled up a 23-year high in April. Just as housing affected trade on Friday, it will no doubt have some impact today with the release of April new home sales due at 10:00 a.m. EDT. Economists expect the report to show yet another decline.
Also at the same time, May consumer confidence is due and is also expected to edge lower.

And, of course, the ever (recently) rising oil prices. While no new highs have registered over the weekend, crude prices held above $133 a barrel Tuesday, supported by supply concerns and worries about the health of the U.S. economy and hence the outlook for the U.S. dollar. A militant attack on a pipeline in Nigeria didn't help matters either.