WASHINGTON (Reuters) - U.S. President Donald Trump said on Sunday he would allow the federal government to shut down if Democrats do not fund his border wall and back immigration law changes, betting that maintaining a hard line will work in Republicans’ favor in November congressional elections.

However, a disruption in federal government operations could backfire on Trump if voters blame Republicans, who control Congress, for the interruption in services.

“I would be willing to ‘shut down’ government if the Democrats do not give us the votes for Border Security, which includes the Wall! Must get rid of Lottery, Catch & Release etc. and finally go to system of Immigration based on MERIT! We need great people coming into our Country!” Trump said on Twitter.

Americans are divided along party lines on immigration, and 81 percent of Republicans approved Trump’s handling of the issue, according to a Reuters/Ipsos poll released this month.

The Republican president has threatened a shutdown several times since taking office in 2017 in a bid to get immigration priorities in congressional spending bills, especially funding for a wall along the southern U.S. border. Trump has asked for $25 billion to build the wall.

“I don’t think it would be helpful, so let’s try to avoid it,” Republican Senator Ron Johnson, chairman of the Senate Homeland Security Committee, said on CBS’ “Face the Nation.”

Congress must agree on a spending measure to fund the government by a Sept. 30 deadline.

Although Republicans control both the U.S. Senate and House of Representatives, disagreements between moderates and conservatives in the party have impeded a speedy legislative fix.

Standoffs over spending levels and immigration led to a three-day government shutdown, mostly over a weekend, in January and an hours-long shutdown in February.

The House in June rejected an immigration bill favored by conservative Republicans.

The Republican president has made tougher immigration laws a centerpiece of his administration, from the first ill-fated travel ban on people from predominantly Muslim nations to the current battle raging over the separation of illegal immigrant children from their parents at the U.S.-Mexico border.

A federal judge on Friday urged the U.S. government to focus on finding deported immigrant parents whose children remain in the United States.