President Trump on Wednesday expressed optimism in his effort to build a wall along the U.S.-Mexico border and said recent court victories will help pave a way around “obstructionist Democrats.”

Building the wall was a key promise during Trump's 2016 presidential campaign but he has struggled to secure congressional support for the project -- a problem made worse for him when Democrats took control of the House after the 2018 midterm elections. Now the president appears intent on preventing his 2020 Democratic challenger from framing the issue as an unfulfilled promise.

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"The Wall is going up very fast despite total Obstruction by Democrats in Congress, and elsewhere," Trump tweeted.

Trump promised to have close to 500 miles of wall along the 1,954-mile-long border with Mexico. The U.S. Supreme Court in July cleared the way for about $2.5 billion to be used from a Pentagon counter-drug program.

The Trump administration says the wall is important in keeping out people who cross illegally.

Critics say a wall is useless. They say most of those apprehended turn themselves in to Border Patrol agents in the hope they can be eventually released while their cases play out in immigration court.

Sen. Elizabeth Warren, D-Mass., a top 2020 Democratic hopeful, said on Twitter in March that the border wall is not about security. She said, “it’s a monument of hate and division, and I won’t support it.”

The Supreme Court on Wednesday also issued an order against lower court injunctions that blocked the White House’s ban on asylum for anyone trying to enter the U.S. by traveling through a third country. The order was not the final ruling but was seen as a victory for Trump. Only liberal Justices Sonia Sotomayor and Ruth Bader Ginsburg dissented.

Victor Manjarrez Jr., a former Border Patrol chief who’s now a professor at the University of Texas, El Paso, spoke to the Associated Press and said tall border fencing is crucial in some areas and less helpful in others, like remote stretches of desert where shorter barriers and more technology like ground sensors would suffice.

He said building 450 to 500 miles of fence by the end of next year would be tough if that figure doesn’t include sections of the wall that have been built recently.

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“As it stands now, contractors are building pretty fast,” Manjarrez said. The real question is whether the government needs to build that much fencing, he said.

Fox News' Gregg Re and the Associated Press contributed to this report.