The trust is partnering Manchester and Sheffield City Councils on one of the Rethinking Parks projects funded by Nesta in July - looking at endowments and volunteers. It already works closely with Manchester on volunteer programmes through its first urban gardener, Sean Harkin.
Trust leaders said they were committed to helping urban parks "to be more viable" at a launch media briefing. Director-general Dame Helen Ghosh said plans are "at an embryonic stage" but returned to trust founder Octavia Hill's commitment to provide "outdoor sitting rooms" for the poor.
"When you ask people what they most care about, they say local green space," she added. "They (local authorities) are saying they will not have money for discretionary services - they will let them run down, become shabby.
"There's a real risk that we end up looking after these (National Trust) oases of beauty. There's no point doing oasis management." She ruled out "taking over the parks in big cities" because the trust "couldn't afford it".
After the launch, project leader and trust regional director Harry Bowell said: "Our project aims to harness the huge value and benefits that parks provide to demonstrate the potential of endowments in securing the future for public parks for everyone. We're excited by the project."
The trust sees climate change as "the single biggest threat" to its estate. The strategy has a renewed focus on landscape conservation and restoration, wildlife and climate change mitigation - including challenging farmers and growers to develop more sustainable methods - and heating its mansions with biomass boilers.
Trust chairman Tim Parker said he wants to drive people from their screens to the "marvellous largesse of quite varied and beautiful landscapes" the trust owns.