New York City Mayor Bill de Blasio reminded state lawmakers Monday that President Donald Trump’s policies could prove hostile to the boroughs and urged them to empower the city to bolster its resources and fend for itself.

While testifying at a joint state Senate and Assembly hearing on Gov. Andrew Cuomo’s budget proposal, de Blasio said the state should allow the city to enact a so-called mansion tax on high-value home sales, to streamline its construction contracting with the “design-build” model and to consider his administration’s vision for a lucrative property tax abatement.

“We are quite clear that any actions taken in Washington could create real pain for both state and city government,” de Blasio said. “That’s why it’s so important that we ask your support in making sure that the state budget insulates and protects local governments and our work given these great uncertainties.”

De Blasio said he anticipates wealthy New Yorkers having to pay less in federal taxes, so it would be fair for them to pay more locally under a so-called mansion tax. If approved in Albany, de Blasio’s administration said it would institute a 2.5 percent tax on condo, co-op and one-to-three family home sales that exceed $2 million. The administration believes this would affect some 4,500 transactions over the coming fiscal year, generating $336 million that would be used to secure affordable homes for some 25,000 low-income senior citizens. A similar de Blasio proposal faltered in Albany in 2015.

“In this uncertain federal climate, identifying local revenue sources for affordable housing preservation is paramount,” de Blasio said. “I think it’s fair to say one of the areas most threatened by potential federal budget cuts is affordable housing, public housing, Section 8 – all the things that so many of our residents in New York City and across the state depend on to be able to afford to live.”

Tenant activists have voiced concerns about those federal funding streams drying up, and cited them as a reason to prioritize proven, cost-effective affordable housing strategies, rather than Cuomo’s plan to revive 421a incentives. The governor’s proposal is widely expected to drive up the cost of 421a, a now-lapsed property tax abatement previously offered as an incentive for developers to set aside a portion of residential projects for below-market apartments.

Tom Waters, a housing policy analyst with Community Service Society of New York and a member of the Alliance for Tenant Power, said Cuomo’s 421a plan may cost the city $2.4 billion in lost revenue. At the same time, he said the current bill language also cuts into the city’s ability to influence how the benefit is administered – or to opt out of the 421a program all together.

De Blasio did not mention any changes to the city’s authority over 421a during his testimony on Monday. Instead he took a more conciliatory tone, telling lawmakers he was ready for a conversation about how to improve the governor’s proposal.

Yet the mayor said that the budget made a “glaring and inexplicable omission” in not including New York City among the several state agencies and counties authorized to use design-build construction. He said the city could immediately save $450 million if permitted to use the project delivery technique, which allows the government to sign a contract for both the design and construction of a project rather than bidding both stages out separately.

The state is also sitting on education and housing funding meant for the city, de Blasio argued. Specifically, he called for lawmakers to sign a memorandum of understanding on how to use $2 billion allocated in the last state budget for affordable and supportive housing, and to comply with the landmark Campaign for Fiscal Equity legal settlement that de Blasio contended entitles the city to $1.6 billion more in education funding.

Some Republican lawmakers questioned de Blasio’s ability to effectively oversee child welfare, education and other programs and services that depend on state funding. And de Blasio’s decision to risk federal funding by resisting some of Trump’s immigration directives came under fire from Republican Assembly members Nicole Malliotakis and Ron Castorina Jr., who are in court challenging the city’s decision to destroy records of undocumented immigrants’ and others’ who received municipal IDs from the city.

But perhaps the most testy exchanges revolved around the city’s plan to impose a 5-cent fee on single-use bags. State Sen. Simcha Felder of Brooklyn accused the mayor of refusing to explore, non-punitive alternatives. In a dramatic display, Felder pulled out a loaf of bread and jug of milk, and asked the mayor if he knew how expensive everyday groceries can be – giving everyone a glimpse in just how controversial the mayor’s tax proposals may prove in Albany.

“This is a 99 percent tax on the 99 percent,” said Felder, a Democrat who caucuses with the Republicans. “It’s a credit for the 1 percent, because the people who have limousines, chauffeurs, nannies are not dragging their groceries. They’re getting them delivered or brought home by somebody else.”