Asked whether Trump would sign the deal being hammered out by U.S. lawmakers, Sarah Sanders said in an interview that the president needed to see the final agreement before making a decision.
"There are some positives in this bill, but it's certainly not enough," Sanders said. "The president and his team have been looking at every option possible to get the full funding they need in order to complete the wall."
Congress faces a tight deadline to pass legislation to avert another U.S. government shutdown. Several news outlets reported Trump planned to sign the deal.
Several news outlets reported that Trump intended to sign the measure into law if it passes Congress. Representatives for the White House did not immediately respond to a request for comment on those reports.
Trump on Tuesday, however, did not rule out vetoing the legislation and said he was not happy with the deal, which denies him funds for his U.S.-Mexico border wall. But he also said he did not expect another shutdown.
The Democratic-controlled U.S. House of Representatives could vote as soon as Wednesday evening, a senior aide said, despite not yet having produced a written copy of the agreement reached by congressional negotiators on Monday night.
Congressional sources said the deal includes $1.37 billion for new border fencing, about the same as last year - along 90 km of the border - but not the $5.7 billion Trump has demanded to help build his promised border wall.
The president previously threatened to declare a "national emergency" if Congress did not provide money specifically for the wall -- a move that would almost certainly draw opposition in Congress and in the courts.
Trump made the wall a central 2016 campaign promise, calling it necessary to combat illegal immigration and drug trafficking. He said Mexico would pay for it, but Mexican officials rejected that. Democrats have called a wall expensive, ineffective and immoral.