Los Angeles (CNN) Even before President Donald Trump arrived in California on Tuesday, his administration issued yet another pre-emptive strike at the state that likes to pride itself as the center of the resistance to his agenda.

Following vague threats that his administration might seek to commandeer what Trump views as the state's feckless response to its homeless crisis , White House officials also signaled a second battle on the environmental front -- doing away with the state's right to put in place more stringent vehicle emissions standards than the federal government.

Even with that threat looming, California's leaders have taken a softer approach on the homeless crisis gripping the Golden State. Still, leaders here are concerned that a heavy-handed intervention from the Trump administration could upend carefully calibrated plans for building thousands of new units of affordable housing and wrap-around-services for those living on the streets.

Trump made his way to the Bay Area for a West Coast swing that is expected to net as much as $15 million in campaign fundraising. He took the opportunity to weigh in the state's homeless crisis -- namely the nuisance that businesses and high-dollar tenants must deal with as homeless Californians erect tents on sidewalks and in the doorways of corporations and businesses.

'They can't believe what's happening'

"We can't let Los Angeles, San Francisco and numerous other cities destroy themselves by allowing what's happening. And I'm speaking to tenants -- in some cases foreign people ... where they're tenants in buildings throughout various cities in California, and other places ... where they want to leave the country. They can't believe what's happening," Trump told reporters on Air Force One.

"We have people living in our ... best highways, our best streets, our best entrances to buildings and pay tremendous taxes," Trump added, noting they are places "where people in those buildings pay tremendous taxes, where they went to those locations because of the prestige."

The President said that he would work with Housing Secretary Ben Carson to confront the issue. "The people of San Francisco are fed up, and the people of Los Angeles are fed up. And we're looking at it, and we'll be doing something about it," Trump said as he was flying to the Bay Area for a fundraiser.

At a separate event, Carson was vague when asked whether the administration's plans would use police to get homeless people off the street and into federal facilities.

"The policy includes being logical and looking at things that work and are effective and looking at best practices wherever they exist around the world and trying to be fair to all the people. That's what the policy entails," he said on Tuesday.

Before Trump arrived, several top California leaders extended an olive branch, hoping to persuade him to join with them in building out an effective strategy for getting the homeless housed across the Golden State.

It is still unclear what the administration plans to do about the half-million Americans who are living on the street on any given night. But on Monday, the acting chairman of the Council of Economic Advisers, Tomas Philipson, highlighted the Trump administration's efforts to remove "government barriers in the housing market" that he said "limit supply and thereby raises prices" for housing that lead to Americans ending up on the streets.

Philipson noted that 47% of the nation's homeless population lives in California (though the state accounts for 12% of the nation's population). One-fifth of the entire homeless population is living in Los Angeles County.

"Harmful local government policies in select cities, along with ineffective federal government policies of prior administrations, have exaggerated the homelessness problem," Philipson said. "The Trump administration is working to reverse the failed policies of the past, and instead implement policies that address the underlying causes of homelessness."

A plea

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On Tuesday, Los Angeles Mayor Eric Garcetti, a Democrat, shot a video from South Los Angeles at the city's newest "Bridge Home" shelter -- a series of 26 temporary shelters that the city is building to address the massive bed shortage in LA for those living on the streets.

In the video message marking the arrival of the commander in chief in California, Garcetti addressed the President directly, commending him for his interest in addressing LA's homeless crisis.

"I wanted to talk to the President today because he has shown an interest in the issue of homelessness," Garcetti said in a plea for more federal resources, as he filmed the interior of the new shelter which has individual pods that have beds, cabinets and even cages for LA's homeless to house their pets.

"It's no secret that I've disagreed with you on almost everything, Mr. President, but if you are, in your heart, willing to save lives alongside us, we know what works here," Garcetti said. "It is time for us to pause politics and not to demonize Americans who are on the street."

Garcetti added that the rate of homelessness in Washington, DC, "in the backyard of the White House" is even higher than here in LA. The report released Monday by Trump's Council of Economic Advisers noted DC has the highest overall rate of homelessness among cities: 103 per 10,000 people compared with the national average of 17 homeless people per 10,000. (Boston, New York City, San Francisco were the second, third and fourth highest among cities, respectively).

Last week, Garcetti sent Trump a letter thanking him for a visit that Trump administration staff made to learn about the efforts that are underway in Los Angeles to provide temporary and permanent housing to those living on the city's streets.

He noted that city and county voters have approved two ballot measures to expand homeless services by $4.5 billion over a decade. In 2014, Los Angeles moved 9,000 homeless people into housing. By comparison in 2018, that number was 21,000.

Garcetti also wrote that the federal government cut HUD funding for the production of new housing and preservation by 31% during the period between 2016 and 2018, according to the Center for Budget and Policy Priorities.

Frequent foe

In a letter to Trump on Monday, Democratic California Gov. Gavin Newsom -- who frequently spars with the President -- sent him a letter outlining potential White House steps that his administration believes would do the most to ameliorate the problem in the Golden State.

Newsom asked Trump to provide 50,000 more vouchers through federal programs that provide rental subsidies for extremely low-income Americans, while increasing the value of those vouchers to meet the high cost of rent, particularly in California.

The California governor also asked the Trump administration to work with his administration on a program to incentivize landlords to work with voucher holders to find stable housing.

"Shelter solves sleep, but only housing solves homelessness," Newsom wrote to the President. "Pairing more vouchers with an increase in the fair market rent value of the vouchers, you have the ability to make a meaningful difference in the lives of so many who suffer on our streets. These federal programs have a track record of success when implemented properly and we urge you to consider this request in good faith."

On the environmental front, just as Trump prepared to arrive in San Francisco, CNN learned that the Environmental Protection Agency is preparing to revoke the state's authority to set vehicle emission standards and may make a statement to that effect as early as Wednesday.

Trump's western swing began at a San Francisco lunch expected to net $3 million for Trump Victory, the joint fundraising committee for the Republican National Committee and his campaign. On Tuesday evening, he heads to Beverly Hills for a dinner that will bring in $5 million. His final events on Thursday will be a breakfast in Los Angeles ($3 million) and a lunch in San Diego ($4 million).