Republican lawmakers were reportedly underwhelmed by a White House plan for immigration reform, which was spearheaded by Jared Kushner, President Donald Trump's son-in-law.

He was unable to answer key questions about the plan, leaving Stephen Miller, a senior White House adviser and immigration hard-liner, to explain the proposal, The Washington Post reported Tuesday night.

Kushner even reportedly said his plan would not address the fate of hundreds of thousands of young immigrants protected under the Deferred Action for Childhood Arrivals program — a crucial component to winning over Democratic support.

GOP senators such as Lindsey Graham and Mitt Romney said the plan catered to Republicans but would fail to garner votes from Democrats.

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Republican senators are reportedly less than impressed by a White House plan to overhaul the US immigration system, which left gaping holes on major issues such as the future of the young immigrants protected under the Deferred Action for Childhood Arrivals program.

The lawmakers met on Tuesday with the White House senior advisers Jared Kushner and Stephen Miller to go over the plan, which CNN reported would be unveiled on Thursday.

Kushner, President Donald Trump's son-in-law, has been working behind the scenes for months to create an immigration proposal that can both crack down on border security and prioritize high-skilled immigrants in a "merit-based" system.

But Republican officials told The Washington Post that Kushner was unable to answer a number of questions about his own plan. Instead, Miller, a staunch immigration hard-liner, stepped in to answer lawmakers' queries and at times interrupted Kushner, according to The Post.

"[Kushner's] in his own little world," one person familiar with the meeting told The Post. "He didn't give many details … And there were a number of instances where people had to step in and answer questions because he couldn't."

The White House did not immediately respond to INSIDER's request for comment on the reports.

Demonstrators rally in support of Deferred Action for Childhood Arrivals (DACA) outside the Capitol on January 21, 2018. Associated Press/Jose Luis Magana

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The meeting left lawmakers pessimistic about the plan's chances in Congress, where it would need Democratic votes, according to The Post.

Kushner even said at one point that the plan would not address the fate of the Deferred Action for Childhood Arrivals program, one of the key immigration issues the government is facing, and one that is vital to winning over Democratic support, according to the Post.

The Obama-era program shields roughly 700,000 young immigrants from deportation and has been in limbo for more than a year after federal courts prevented the Trump administration from fully terminating the program in September 2017.

Republican senators emphasize how any immigration plan needs to appeal to Democrats, too

Republican Sen. Susan Collins of Maine later told The Associated Press that immigrants protected under DACA "cannot be excluded from any immigration package."

Stephen Miller after the meeting with Senate Republicans on May 14, 2019. Associated Press/J. Scott Applewhite

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"I think folks in the room were underwhelmed," one official told CNN. But another official told the network it was "wrong" to characterize Kushner as unfamiliar with the subject matter.

Some Republicans have since expressed tepid support for Kushner's ideas, while still expressing doubts that he could win over Democrats.

"I don't think it's designed to get Democratic support as much as it is to unify the Republican Party around border security," Sen. Lindsey Graham, a South Carolina Republican, told NBC News.

"I thought it was a very effective presentation," Sen. Mitt Romney of Utah told The Post. "It would have passed with flying colors among Republicans. But we need to get some Democrats, too."