President Donald Trump on Saturday launched a new salvo in the fierce battle over immigration, blasting Democrats for obstructing his efforts to secure the border as thousands of Central American migrants flooded the dividing line between the U.S. and Mexico.

Amid worsening tensions in the White House over refugees from Guatemala and Honduras flocking to the border, Trump took to Twitter and blamed Democrats for being weak on border security. Calling attention to the "horrors taking place on the border," the president urged Senate Minority Leader Chuck Schumer, D-New York, and House Minority Leader Nancy Pelosi, D-California, to work with the White House on a solution.

If the Democrats would stop being obstructionists and come together, we could write up and agree to new immigration laws in less than one hour. Look at the needless pain and suffering that they are causing. Look at the horrors taking place on the Border. Chuck & Nancy, call me!

With the November midterms just 17 days away, Trump has become more vocal about the border crisis. At an election rally on Friday in front of thousands of supporters in Arizona, a state bordered by Mexico.

"Democrats want to throw your borders wide open to criminals. I want to build a wall," Trump told the crowd. "The Democrats don't care that a flood of illegal immigration is going to bankrupt our country."

The president held a rally in rural Nevada on Saturday afternoon. Meanwhile, former Vice President Joe Biden was also in Nevada, headlining a get-out-the vote rally for Democrats in Las Vegas.

The president and Republicans are trying to fire up their base ahead of next month's hotly-contested election, in an effort to stave off a possible "blue wave" that could see Democrats elected in large numbers.

Trump has reportedly become frustrated by efforts to stymie his tough stance on immigration, an issue that launched his 2016 election bid. Several publications this week reported an expletive-filled shouting match between White House Chief of Staff John Kelly and National Security Adviser John Bolton over the issue, sparking new concerns Kelly could resign.

In September, the president signed a spending bill to keep the government open, despite previously calling the measure "ridiculous" because it did not include funding for a wall along the southern border. White House budget director Mick Mulvaney told CNBC shortly after the House followed the Senate in passing the funding measure that the administration would take up the wall issue after the midterms.