The US government has expressed concerns to the South Korean government about the 4G network contract awarded by local operator LG Uplus to Huawei, according to local media.

This latest exertion of pressure follows a letter in December written by two influential US senators to senior officials in the Obama administration which laid out their worries over the Chinese vendor’s contract win.

Now the US has raised its concerns directly with the Korean government, according to Korea JoongAng Daily. The two countries have a close strategic alliance which includes a substantial US military presence in the country.

“It is true that the US has made an issue [out of Huawei advancing into Korea], but it is a basically a trade and business deal,” said a source.

Last week, The Daily Beast reported that US Vice President had voiced concerns with Korean Prime Minister Jung Hong-won during a visit in December.

In addition, the administration’s National Security staff have asked US intelligence services to study the security implications of the LG Uplus-Huawei deal.

However, it appears from the Korean government’s tone it is sticking to a line that the contract award is a business decision that should sit outside US-Korea relations.

The original LTE contract was awarded by LG Uplus to Huawei in October 2013.