A boy tries to squeeze through the border fence in Playas de Tijuana, Mexico, in this Feb. 6, 2017 file photo. (Xinhua/Dan Hang)

WASHINGTON, Dec. 11 (Xinhua) -- U.S. President Donald Trump said Tuesday he will have the military build his promised wall on the U.S.-Mexico border if Democrats in Congress block the legislation approving the funding for the project.

Trump made the threat in a series of tweets hours before a scheduled meeting with Senate Democratic Leader Chuck Schumer and House Democratic Leader Nancy Pelosi.

"If the Democrats do not give us the votes to secure our Country, the Military will build the remaining sections of the Wall. They know how important it is!" he said.

The president said thousands of National Guard troops and active-duty military troops he deployed on the U.S. southern border "have done a FANTASTIC job," nonetheless stressing that "A Great Wall would be, however, a far easier & less expensive solution."

The meeting with Schumer and Pelosi, which Trump said he looked forward to, is meant to avoid a potential partial government shutdown as funding for a number of federal agencies will expire on Dec. 21.

Trump supported Pelosi's bid for House Speaker right after the midterm elections in November, but this time he criticized her and Schumer for opposing the border wall "for strictly political reasons," adding that they "do NOT want Border Security" and instead "want Open Borders for anyone to come in."

"They will fight it at all cost, and Nancy must get votes for Speaker. But the Wall will get built," the president vowed.

Trump has been asking Congress to include at least 5 billion U.S. dollars for the wall in the next funding package, something the Democrats have squarely rejected.

Schumer and Pelosi issued a statement Monday saying the United States "cannot afford a Trump shutdown." They said Trump "knows full well that his wall proposal does not have the votes to pass the House and Senate and should not be an obstacle to a bipartisan agreement."

Trump promised to build the wall during his presidential campaign in 2016, but his handling of migrants seeking to enter the United States via the southern border has been put a question mark.

During a conference call on Monday, reporters challenged an official of the U.S. Customs and Border Protection by asking why the country was able to send troops and construct temporary shelters along the border but unable to double down on its effort to process more asylum seekers.

The official, who spoke on condition of anonymity, said improving asylum claims will sacrifice other priorities such as national security and drug interdiction.

"To shift resources away from those other competing priorities so that we would process more migrants ...does come at a negative impact on those other missions," the official said.