By Richard Cowan

WASHINGTON (Reuters) – U.S. Senate Republicans on Tuesday turned up the heat on Democrats seeking protections for young “Dreamer” immigrants as Senate Majority Leader Mitch McConnell embraced President Donald Trump’s demands for broad changes to the country’s immigration policies.

In announcing his support for legislation that would help immigrants who were brought illegally to the United States as children, McConnell also threw his weight behind building a U.S.-Mexico border wall and sharply curtailing visas for the parents and siblings of immigrants living in the United States legally.

“This proposal has my support and during this week of fair debate I believe it deserves support of every senator who’s ready to move beyond making points and actually making a law,” McConnell, a Republican, said in a speech on the Senate floor.

Even some Republicans, however, have expressed skepticism that such broad, fundamental changes in U.S. immigration law can pass the Senate by the Thursday deadline that No. 2 Republican Senator John Cornyn urged late on Monday.

Also on Monday, Democratic Senator Dick Durbin, who is leading the charge for Dreamers, told reporters that he thought early Senate votes on immigration legislation would begin with “expansive” measures that will fail to win the 60 votes needed to clear procedural hurdles.

Then, Durbin said, senators will be forced to move “toward the center with a moderate approach.”

But at least for now, Republicans were holding a tough line. Republican Senator Tom Cotton, interviewed on Fox News, said Trump’s immigration plan “is not an opening bid for negotiations. It’s a best and final offer.”

That ran counter to statements Trump has made in recent days, including early on Tuesday in which he said in a tweet that “Negotiations on DACA have begun.”

DACA is the Deferred Action for Childhood Arrivals program, which Democratic former President Barack Obama initiated in 2012 and which has allowed around 700,000 Dreamers to legally study and work in the United States temporarily. Last September, Trump announced he would terminate the program on March 5.

During testimony before the Senate Budget Committee on Monday, White House Budget Director Mick Mulvaney said he thought that a deal on immigration legislation will be reached “and that we have full funding on the (border) wall” of $18 billion over two years.

Durbin and other Democrats have talked of the possibility of a bill that provides for a pathway to citizenship for Dreamers and additional border security, which could include the construction of more border fencing and other high-tech tools to deter illegal immigrants.

(Reporting By Richard Cowan, additional reporting by Katanga Johnson; Editing by Bernadette Baum and Jonathan Oatis)