Sen. John Cornyn (R-Texas), the No. 2 Republican in the Senate, criticized President Trump's proposal to raise the minimum age for gun purchases, saying it wouldn't "save lives."

"I think what we want to focus on is things that will actually save lives," Cornyn said Friday, according to CNN. "That's why I think the focus should be on the Fix [National Instant Criminal Background Check System] bill, which is the only bipartisan piece of legislation that can be signed into law."

Cornyn said a bill increasing the minimum age to purchase guns, which Trump endorsed earlier this week, would be "difficult to enforce."

"I'm not sure why we would go to those lengths when I don't think that gets to the root of the problem," he said.

Cornyn has co-authored a bill with Sen. Chris Murphy (D-Conn.) that would strengthen the federal background check system by requiring states and federal agencies to produce plans to report offenses that would bar people from passing a check needed to purchase a firearm.

The bill also reiterates that federal agencies must report all violations to the National Instant Criminal Background Check system and creates new financial incentives for states to report information.

The proposal is a rare piece of gun legislation endorsed by the National Rifle Association, and earlier this week White House press secretary Sarah Huckabee Sanders issued a statement saying Trump supports the deal.

In a Thursday tweet, Trump vowed to push for comprehensive background checks for gun sales, while calling for the minimum purchase age to be raised to 21.

The president has also ordered the ban of bump stocks, which are used to increase a weapon's rate of fire.

Trump has also suggested arming teachers and schools officials, a highly controversial proposal that has drawn criticism from both sides of the aisle.