U.S. stocks are up sharply at midday, giving them a strong start to February after their biggest January in 15 years.

At midday, the Dow Jones industrial average is up 139 points, or 1 percent, to 12,771. The broader Standard & Poor's 500 index is up 14 points, or 1 percent, to 1,327. The Nasdaq composite is up 1 percent to 2,844.

Strong manufacturing data and positive signals from Greece helped stocks.

A key manufacturing index shows that U.S. factories raised output in January by the most in seven months. And the Commerce Department says construction spending rose 1.5 percent in December, for the fifth monthly gain in a row.

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