WASHINGTON (Reuters) - A Pentagon-led review ordered by President Donald Trump has identified hundreds of instances where the US military depends on foreign countries, especially China, for critical materials, US officials said.

The study is expected to be released in the coming weeks and aims to lessen the US military's reliance on foreign countries and strengthen US industry.

Among the study's conclusions will be a determination the United States is too dependent on foreign suppliers for a range of items including some micro-electronics, tiny components such as integrated circuits and transistors, the officials told Reuters on condition of anonymity.

These kinds of essential components are embedded in advanced electronics used in everything from satellites and cruise missiles to drones and cellphones.

The focus on China reflects an effort under Trump to address the risks to US national security from Beijing's growing military and economic clout. Pentagon officials want to be sure China is not able to hobble America's military by cutting off supplies of materials or by sabotaging technology it exports.

The report could add to mounting trade tensions with China, bolstering the Trump administration's "Buy American" initiative, which aims to help drum up billions of dollars more in arms sales for US manufacturers and create more jobs.

Lt. Col. Mike Andrews, a Pentagon spokesman, did not comment on the contents of the report but told Reuters the study would make recommendations "to ensure a robust, resilient, secure and ready manufacturing and defense industrial base."

US soldiers secure an area under the aurora borealis during night live-fire training at Fort Greely, Alaska, October 25, 2016. US Department of Defense

China, which has also become the main supplier of many of the rare earth minerals used by the United States, will be given special emphasis in the report, said the officials who spoke to Reuters on condition of anonymity.

A January analysis from the United States Geological Survey said the United States produced no rare earth minerals in 2017 while China accounted for 81% of global mine production. Rare earth minerals are used in magnets, radars and consumer electronics.

Aside from the risk that a foreign power could cut off vital supplies needed to keep the US military up and running, other risks include the threat of sabotaged equipment or espionage.

The Pentagon has long fretted that "kill switches" could be embedded in transistors that could turn off sensitive US systems in a conflict. US intelligence officials also warned this year about the possibility China could use Chinese-made mobile phones and network equipment to spy on Americans.

When the study is released, it will not provide a detailed inventory of all of the weaknesses in the supply chain. These will be in a classified annex.

A US official said the report will also examine US shortcomings that contribute to purchases from foreign companies, including roller-coaster US defense budgets that make it difficult for companies to predict government demand. Another weakness is in US science and technology education.

Bolstering US industry

US soldiers load an AGM-114 Hellfire missile on an AH-64E Apache helicopter in Kunduz, Afghanistan, May 31, 2017. US Army

Advocates of the study say it is a late but critical look at ways to address America's loss of manufacturing, whose toll on national security gets far less attention than the jobs lost, and the political wave that it created in rust-belt states that helped elect Trump president in 2016.

"People used to think you could outsource the manufacturing base without any repercussions (on national security). But now we know that's not the case," said one US official familiar with the report, speaking on condition of anonymity.

One aspect of the report's recommendation is expected to be ensuring profitability for niche US producers of critical components in American weaponry.

Ellen Lord, the Pentagon's top weapons buyer, has publicly spoken in recent weeks about the Defense Production Act (DPA) of 1950, which allows the US president to incentivize domestic producers of critical materials through purchase commitments and other guarantees.

Lord said the government should step in to offer such support if businesses would be unable to ensure a "reasonable profit."

The US Government Accountability Office offered one example in a report last year about how the US military had to fund a US factory in 2014 to produce the chemical Butanetriol, used in the Hellfire air-to-surface missile.

For the previous six years, the military relied on China for the chemical.

(Reporting by Phil Stewart and Mike Stone; editing by Chris Sanders and Frances Kerry)