NEW YORK/LOS ANGELES: Columbia University students heckled House Speaker Mike Johnson on Wednesday as he visited the flashpoint of nationwide student demonstrations over the Israeli war in Gaza, even as the New York school agreed to 48 more hours of negotiations to end a protest encampment.

Johnson's visit, which he said was meant to support Jewish students intimidated by some anti-Israeli demonstrators, took place shortly after the university extended a deadline from Wednesday morning to Friday morning to reach an agreement to remove an encampment that has come to symbolize the campus protest movement.

Some of the campus protests taking place coast to coast were met with shows of force from law enforcement.

In Texas on Wednesday, state highway patrol troopers in riot gear and police on horseback broke up a protest at the University of Texas in Austin and arrested 20 people.

The University of Southern California declared its campus closed and asked the Los Angeles Police Department to clear a demonstration. Police arrested students who peacefully surrendered one-by-one, hours after campus police who took down an encampment were overwhelmed by protesters and requested LAPD help.

Other demonstrations took place at Brown University in Providence, Rhode Island, the University of Michigan in Ann Arbor, Massachusetts Institute of Technology in Cambridge and California State Polytechnic in Humboldt.

Protesting students have demanded universities divest assets from Israel and seek to pressure the U.S. government to rein in Israeli strikes on Palestinian civilians.

Israel's fierce response followed a deadly Oct. 7 cross-border raid by Islamist militants from Hamas, which controls the Gaza enclave.

The at times vulgar heckling and booing that greeted Johnson did not drown him out, though he was hard to hear because he spoke to media microphones, not through loudspeakers.

"As Columbia has allowed these lawless radicals and agitators to take over, the virus of antisemitism has spread across other campuses," Johnson said from the steps of the university library, calling on violent protesters to be arrested and threatening to cut off federal funding to universities that fail impose order.

Johnson, whose job as House Speaker has been threatened by ultraconservative Republicans in his caucus, could have expected a cold welcome from students on a New York City campus known as a liberal bastion.

In a politically polarized country, conservatives can score points by being seen as standing up to liberal activists, many of whom say the Republican portrayals of anti-semitic violence on campus are greatly exaggerated for political purposes.

Johnson also met with Jewish students who said they were fearful to come onto the campus, citing testimony from Jewish students who said they had been spat on and seen swastikas drawn on the walls.

Before his press conference, Johnson met with about 40 Jewish students on campus, according to students who were there.

Students at the encampment say their protest has been peaceful, and that outsiders not connected with their movement are behind any inflammatory confrontations off-campus.

"We regret that there's no attention on this peaceful movement and politicians are diverting attention from the real issues," said Mahmoud Khalil, a Palestinian student at Columbia who has been part of the negotiations with school administration.

Free speech advocates PEN America called the sudden escalation at the University of Texas "deeply alarming."

"The administration should be doing everything in their power to keep their students safe and the campus operating, but calling the state police to disperse a peaceful protest that had barely begun does the opposite," Kristen Shahverdian, PEN's campus free speech program director, said in a statement.

The political reverberations reached the White House, where press secretary Karine Jean-Pierre said President Joe Biden believes free speech, debate and nondiscrimination are important on college campuses.

"We want to see this be peaceful," Jean-Pierre said in Wednesday's press briefing. "It is important that students feel safe ... It should not be violent, it should not be hateful rhetoric." (Reporting by Jonathan Allen in New York, Jane Ross in Los Angeles, Brendan O'Brien in Chicago, Trevor Hunnicutt and Kanishka Singh in Washington, and Daniel Trotta in Carlsbad, California; Editing by Deepa Babington and Stephen Coates)