'Phase-out' is good, and you could also use the literal translation 'retirement', which is used by the U.S. Government.

See examples for "retirement of the program":

- PROBING DHS'S BOTCHED MANAGEMENT OF THE ...
https://www.govinfo.gov › content › pkg › html
... its full life cycle, from inception of the program through **design, development, deployment, and operation and maintenance to retirement of the program.**

Upcoming changes to Microsoft Software Assurance Benefitshttps://www.quexcel.com › knowledge-base › upcoming-...
**With the retirement of the program,** Microsoft will also remove Azure training from the catalogue. Planning Services Deployment Planning Services vouchers ...

Lawrence Tech APPR Template
https://www.ltu.edu › attach › APPR-Template-20...DOC
The Chair must specifically address items in Section I-2 that propose **significant program modifications, budget allocations, or retiremen

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With 'phase-out' you don't need 'gradual'. I'm not a fan of 'withdrawal of the program'. Better to say 'closure of the program':

**Program Closure Guidelines** - Millennium Challenge ...
https://www.mcc.gov › resources › doc › guidelines-for...
Oct 8, 2021 — **Closure of the Program must be conducted** in a manner that does not create or leave unresolved any environmental, social, health, or safety ...


**protocol for program closure** - York University Quality ...
https://yuqap.info.yorku.ca › files › 2012/05 › clo...PDF
6.1. Definition. **The protocol for a program closure** includes the closure of degrees and degree programs including credit diplomas and certificates.

COVID-19 EMERGENCY RENTAL ASSISTANCE PROGRAM
https://phlrentassist.org
The **closure of the program** is effective 5:00 p.m. on January 7, 2022. At that time new applications cannot be submitted. New applications will not be ...

US Senator Tammy Duckworth of Illinois
https://www.duckworth.senate.gov › news › press-releases
Jul 23, 2020 — Duckworth Leads Colleagues in Demanding Answers from SBA on **Closure of the Program that Promoted Racial Diversity** in Boardrooms Across the ..