Washington (CNN) Former White House legislative affairs director Marc Short predicted Tuesday that there will be a showdown at the end of the year over funding for President Donald Trump's wall he wants built at the US-Mexico border.

Short said that because September 30 marks the end of the fiscal year, Congress will likely pass a continuing resolution to fund the government, leaving the issue to come up again in December.

"It's been 22 years since Congress actually completed an appropriations process on time. They will likely fail again this year, which means they'll have a continuing resolution to punt this to December," Short, a CNN contributor, said on CNN's "New Day." "I think likely in December is when you'll see the showdown over funding for a wall."

Trump said Monday that he would " have no problem doing a shutdown ," following up on his tweet over the weekend in which he said he would be " willing to 'shut down' government if the Democrats do not give us the votes for Border Security, which includes the Wall."

Congress passed a spending bill in March to fund the government through September 30.

Read More