Current law requires the President to submit his budget for the next fiscal year [2014, in this case] by the first Monday in February. The White House has said that it won't be able to meet that requirement until sometime in March. Congressional Republicans are apoplectic.
Hang on a minute. Current law also requires Congress to pass a budget resolution [not done for three years] and to pass appropriations bills before the October 1 start of the fiscal year [not done since 1997].
I would hate to work at OMB right now. They don't know how much spending will be allowed in 2013 because no appropriations have yet been enacted and the threat of further cuts are likely because of the March 1 sequester. Yet they have to come up with proposals for next year that build on whatever actually happens this year. Lots of luck.