The de Blasio administration is planning to spend $10.4 million to outfit all NYPD patrol cars with bullet-resistant window inserts, according to City Hall officials.

The plan is expected to be announced Tuesday when Mayor de Blasio unveils an $84.7 billion preliminary fiscal 2018 budget — up 3.1 percent from last year’s $82.1 billion preliminary plan.

The NYPD began piloting the inserts in 2016, which protect the back portion of the driver and passenger-side windows but don’t allow the window to be rolled down.

The move followed the killing of two NYPD officers in their patrol vehicle in Brooklyn in late 2014 and the murder of officer Brian Moore in Queens while he rode in an unmarked patrol car.

In July, city officials announced they were allocating $6.8 million to outfit the NYPD’s 3,813 patrol cars with bullet-resistant panels that protect the doors but said they weren’t ready to sign off on the window inserts at the time.

Now they say they’re moving forward using asset forfeiture funds to cover the costs of putting the window panels in every vehicle, with half the money allocated in the current fiscal year and the remainder in fiscal 2018.

“This is about having the backs of our men and women in blue who, with courage and commitment, don the uniform every day to protect and serve,” said City Hall spokesman Austin Finan. “This investment is our commitment to ensuring the safety of those officers on the beat.”

At a New York Building Congress luncheon in midtown Monday, de Blasio also revealed elements of the city’s upcoming capital budget proposal.

He said it would include funding for an additional 1,300 miles of streets to be repaved in the coming fiscal year and a multi-year earmark to create 40,000 new public school seats.