According to press reports, Huawei has been selected as a subcontractor for LG U+ - a Korean subsidiary of LG Corp - in its plans to build a nationwide broadband network in South Korea.

Democratic Senators Robert Menendez, the chairman of the Senate Foreign Relations Committee, and Dianne Feinstein, chairwoman of the Senate Intelligence Committee, said the reports raised concerns in light of the close security alliance between the United States and South Korea.

"Maintaining the integrity of telecommunications infrastructure is critical to the operational effectiveness of this important security alliance," they said in a letter to Secretary of Defense Chuck Hagel, Secretary of State John Kerry and James Clapper, President Barack Obama's Director of National Intelligence.

The letter, dated November 27, was obtained by Reuters on Tuesday. Vice President Joe Biden left on Sunday on a trip to Asia to include stops in China and South Korea, as well as Japan, during which the issue could come up.

The letter underscored how intertwined the communications industry has become with concerns about security.

Last year the U.S. House Intelligence Committee released a report urging U.S. telecommunications companies not to do business with Huawei and its local rival ZTE Corp because it said potential Chinese state influence on the companies posed a security threat.

Both Chinese companies have denied that they have links to the Chinese government.

Menendez and Feinstein said they were "very interested" to receive the administration officials' assessment of "potential threats and security concerns" about Huawei's involvement, as well as any discussions the U.S. government has had with the South Korean government about the importance of network integrity related to the decision.

A senior administration official declined to discuss details of diplomatic discussions involving Seoul, but added, "We do have concerns about Huawei."

The official noted that Huawei was excluded in October 2011 from taking part in the building of a U.S. wireless emergency response network due to national security concerns.

Huawei is the world's second-largest telecom equipment maker.