U.S. President Donald Trump continues to insist that Korea must pay more for the upkeep of U.S. forces here.

That means Seoul faces an uphill struggle in negotiations this week. Its current share of the upkeep of the U.S. Forces Korea amounts to W960.2 billion, about a half of the total (US$1=W1,121).

The Special Measures Agreement, or SMA, a five-year contract between the U.S. and Korea expires at the end of this year.

"Trump, who has sought to reopen global agreements to get what he considers better deals for the U.S., wants [Korea] to pay as much as double the current amount," the Wall Street Journal said citing an unnamed official.

The daily said U.S. Defense Secretary James Mattis and Chairman of the Joint Chiefs of Staff Joseph Dunford have been trying in vain to convince Trump of the importance of the Seoul-Washington alliance beyond financial considerations.

Seoul has little leverage in negotiations since Washington can put pressure on Seoul with automobile tariffs or reduction of USFK troops.

Trump has repeatedly said Seoul is not paying its way since his election campaign two years ago, and the U.S. has urged Seoul to drastically increase its share in nine rounds of talks so far this year.

Seoul's current share based on negotiations in 2014 is only effective until the end of this year, so the two sides must reach agreement this week.

