"We can't let Los Angeles, San Francisco and numerous other cities destroy themselves by allowing what's happening," Trump told reporters aboard Air Force One as he headed to the overwhelmingly Democratic state for a two-day visit.
"And I'm speaking to tenants -- in some cases foreign people, foreign tenants -- but they have, 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, who has ramped up his criticism of California over its homelessness crisis and other issues ahead of the 2020 election, said he was mulling the creation of an "individual task force" to tackle homelessness.
"We have people living in our... best highways, our best streets, our best entrances to buildings... where people in those buildings pay tremendous taxes, where they went to those locations because of the prestige," he said.
"In many cases, they came from other countries and they moved to Los Angeles or they moved to San Francisco because of the prestige of the city, and all of a sudden they have tents.
"Hundreds and hundreds of tents and people living at the entrance to their office building. And they want to leave. And the people of San Francisco are fed up, and the people of Los Angeles are fed up."
Trump, who has previously described the state's homeless crisis as "disgusting," said he planned to discuss the issue with Ben Carson, who heads the Department of Housing and Urban Development.
An estimated 130,000 people are homeless in California, with some 59,000 of them in Los Angeles County.
Trump has threatened a federal crackdown to deal with the problem and last week several officials from his administration visited Los Angeles and met with local officials.