President Obama is seeking an Aug. 1 deadline for overhauling the tax code and making changes to expensive federal health programs, the final pieces of what the administration conceives as a far-reaching plan to rein in the national debt, senior administration officials said Friday.

The proposed deadline was included in a plan Treasury Secretary Timothy F. Geithner delivered to Capitol Hill on Thursday as Obama’s opening bid in talks with congressional Republicans to avert the year-end “fiscal cliff.”