WASHINGTON - US President Donald Trump and congressional Democrats hardened their positions on Thursday over a wall being built on the border with Mexico, raising new doubts over their ability to reach a deal just as negotiations were getting under way.

House of Representatives Speaker Nancy Pelosi told reporters: "There's not going to be any wall money in the legislation" to fund border security for the rest of this year.

Instead, Pelosi said funding for more ports of entry or additional border security technology was open for negotiation.

She added that the 17 House and Senate negotiators should decide the components of the nation's border security.

But the Democratic negotiators went a step further from Pelosi's prohibition on wall funds, unveiling a detailed opening position containing no money for any type of additional physical barriers on the border to control the flow of illegal immigrants and illegal drugs.

Previously, Democrats have supported $1.3 billion for new border fencing this year or improvements to existing fencing.

Asked by reporters about Pelosi's comment on wall funding, Trump, a Republican, said: "Without a wall, it doesn’t work."

"If she doesn’t approve the wall, the rest of it’s just a waste of money and time and energy because it’s desperately needed," Trump told the New York Times in an interview on Thursday.

Congress has a Feb 15 deadline for coming up with a new plan for further securing the southwestern border. Without a deal by then, a partial government shutdown could resume. The president has also said he would consider declaring a national emergency in order to divert existing funds to build a wall, which would almost certainly trigger a constitutional legal challenge.

The bipartisan conference committee of House and Senate lawmakers held a public session on Wednesday with the goal of producing a deal in about a week so it could be voted on by both chambers by the deadline.

TORRENT OF TWEETS

Democratic leaders have called on Trump to stand aside and let the negotiators do their work as a way of fostering success.

Ignoring that advice, Trump issued a series of tweets on Thursday predicting failure and sounding alarms.

"More troops being sent to the Southern Border to stop the attempted Invasion of Illegals, through large Caravans," Trump tweeted. In another tweet, he declared Democrats were becoming the party of "open borders and crime."

At the same time, each side has left some potential openings for the congressional negotiators to exploit.

Evan Hollander, a House Appropriations Committee spokesman, said the Democratic plan detailed on Thursday was the party's "position entering conference negotiations" and "every proposal raised by conferees will be thoughtfully considered."

Pelosi got into a few specifics at her news conference.

"Is there a place for enhanced fencing? Normandy fencing would work. Let them have that discussion," she said, referring to low-slung vehicle barriers.

For his part, Trump, speaking to reporters in the Oval Office, said: "You can have other things" securing the border, "but the other things only really work if you have a physical barrier."

On Capitol Hill, Republican negotiator Senator Richard Shelby did not seem overly concerned about Pelosi's statements, calling them "ambiguous." But he said if Pelosi, Trump and party leaders "would let us, the appropriators, do our job, we could do this."

Calling himself hopeful, Shelby said: "I think if we're going to get a deal, we'll get it probably in the next 10 days."

A Democratic negotiator, Senator Patrick Leahy, brushed aside Trump's tweets, saying people were paying less attention to them.

"A lot of the Republicans told me they wished he (Trump) would not do that," Leahy said.

Trump has demanded $5.7 billion for this fiscal year to start construction on a border wall that he envisioned during his 2016 campaign as being 2,000 miles (3,200 km) long and made of concrete.

Since then, he has said it would not run the full length of the border, could be made of other materials such as steel slats - and that the wall could be called "peaches" if that was a way to get around the semantics of a "wall."

He has also maintained that large sections had already been built.

But on Thursday, Trump reversed himself.

"Lets just call them WALLS from now on and stop playing political games!" he tweeted. "A WALL is a WALL!"

Included in the Democrats' plan was $98 million above last year for US Customs and Border Protection to hire 1,000 more customs agents, and $400 million for buying and deploying security technology.

Reuters