WASHINGTON -- The United States Senate on Tuesday passed a defense bill containing a provision restricting the drawdown of American troops in South Korea.

The Senate voted 86-8 in favor of the National Defense Authorization Act for Fiscal Year 2020, which authorizes $738 billion in funding for the Department of Defense.

The bill will be sent to US President Donald Trump to be signed into law, which Trump said last week he will do "immediately."

The new legislation prohibits the use of funds to reduce the number of American troops stationed in South Korea below the current level of 28,500 unless the US defense secretary certifies that it is in the US national security interest.

The defense secretary must also certify that the reduction will not significantly undermine the security of US allies in the region, and that allies including South Korea and Japan have been appropriately consulted.

The new bar represents an increase of 6,500 from the 22,000 level stipulated in this year's NDAA. If enacted into law, it would limit the Trump administration's ability to use a troop drawdown as a bargaining chip in current negotiations with South Korea on a defense cost-sharing deal.

That possibility was raised in recent South Korean media reports after Washington allegedly demanded a fivefold increase in Seoul's contribution to shared defense costs to nearly $5 billion next year.

Meanwhile, the NDAA also calls for secondary sanctions on financial institutions that conduct business with North Korea in violation of existing sanctions on Pyongyang. The measure would especially affect Chinese banks.

The subsection is billed the Otto Warmbier North Korea Nuclear Sanctions Act of 2019, after the American college student who died in 2017 following more than a year of detention in the North. (Yonhap)