NEW YORK - The U.S. government shutdown, which was in its third day, would be a "relatively small" drag on the U.S. economic expansion in the first quarter, but the effects depend on how long it lasts, Morgan Stanley's analysts said on Monday.

Each week of the shutdown would subtract up to 0.2 percentage point from the annualized quarterly growth rate of the gross domestic product, Morgan Stanley economist Ellen Zentner and strategist Michael Zezas wrote in a research note.