WASHINGTON (Reuters) - The Trump administration has passed a key milestone in a long-delayed rule change that would make it easier to sell U.S. firearms outside the United States, including assault rifles and ammunition, people briefed on the matter told Reuters.

FILE PHOTO: AR-15 rifles are displayed for sale at the Guntoberfest gun show in Oaks, Pennsylvania, U.S., October 6, 2017. REUTERS/Joshua Roberts/File Photo

The proposed rule changes, which would move oversight of commercial firearm exports from the U.S. Department of State to the Department of Commerce, could be enacted as soon as the end of this year, the sources said late on Wednesday.

The move by President Donald Trump's administration may generate business for gun makers such as American Outdoor Brands AOBC.O and Sturm Ruger & Company RGR.N while increasing the sale of deadly weapons abroad. A relaxing of rules could increase foreign gun sales by as much as 20%, the National Shooting Sports Foundation (NSSF) has estimated.

While the State Department is primarily concerned with international threats to stability and maintains tight restrictions on weapons deals, the Commerce Department typically focuses on making it easier for U.S. companies to sell products overseas.

Since taking office, Trump has been a far more outspoken booster of U.S. weapons sales abroad than his recent predecessors, acting almost as a salesman for the U.S. defense industry, analysts have said. Any move that would boost arms sales is also likely to earn enthusiastic support from the influential National Rifle Association as Trump’s re-election campaign heats up.

Critics, including some lawmakers and arms control advocates, have expressed concern that any easing of export rules could make powerful weapons of the type often used in U.S. mass shootings more accessible to criminal gangs and militant groups that Trump has vowed to fight.

“This change will undermine congressional oversight, exacerbate the risk of international gun violence, human rights abuses, and armed conflict, and put U.S. servicemen and women at risk from U.S. weapons that have fallen into the wrong hands,” Rachel Stohl, a managing director at the Washington think tank the Stimson Center, said in a statement.

A review of the rules by multiple U.S. agencies including the Pentagon and the Department of Homeland Security concluded this week, the people said. Government records show the final rule was formally transmitted to the White House Office of Management and Budget on Oct. 23.

This week’s close of the interagency comment period was a key milestone that enables the Trump administration to put lawmakers on notice of the intent to transfer formal oversight to the weapons sales from State to Commerce. Top officials at both departments still need to sign off on the issue before legislators can be notified.

Reuters first reported on the Trump administration's interest in the oversight shift in 2017 here. The action is part of a broader Trump administration overhaul of weapons export policy here.

The effort to streamline U.S. small arms export controls dates back to an Obama administration initiative begun in 2009 that was never translated into policy.

“The move would reduce the regulatory burden and make industry members more competitive in the global marketplace with out reducing oversight,” said Lawrence Keane, head of government and public affairs for the NSSF trade group, adding “there is more oversight at the Commerce Department.”

Representatives from the Commerce Department and budget office declined to comment.

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“The Administration continues to work through the interagency process with the Departments of State, Commerce, Homeland Security, Justice, and other stakeholders to reexamine longstanding polices and regulations to ensure that U.S. industries have every advantage in the global marketplace,” a State Department spokesman said.

The U.S. House of Representatives has passed legislation that would prohibit the transfer of firearms export oversight to the Department of Commerce. But the bill containing the language, an annual defense policy bill called the National Defense Authorization (NDAA), has not passed the Senate and is not yet law.

If the Trump administration moves to notify legislators of the planned change in the coming weeks, it could be enacted before passage of the NDAA, one of the people said.

The Senate’s version of the NDAA does not contain the same language as the House bill. The measure is being discussed by legislative staffs, the person said.

Domestic gun sales have risen in the past three months, according to estimates released on Tuesday by research consultancy Small Arms Analytics & Forecasting. Sales are flat at 10.8 million units when compared to the same period a year earlier, SAAF said in the estimate.