South Korea and the US on Tuesday began a new round of discussions on the shared expenses of their military alliance amid the suspension of their joint drills to facilitate dialogue with North Korea. The meeting, which kicked off in Seoul on Tuesday and will end on Wednesday, marks the fourth round of dialogue between the two countries to try to close the matter before the end of 2018 when the current agreement is expected to expire, Efe news agency reported. The two allies are finding it difficult to agree on what portion of the total cost of maintaining some 28,500 US troops on South Korean territory should be paid by Seoul. The president of the United States, Donald Trump, has been stressing that the expenses borne by Washington for its presence in key countries in the region such as South Korea and Japan in exchange for including them in his security umbrella are very high. According to the latest five-year agreement, Seoul, which began to make small financial contributions in the 1990s, has paid some $865 million for 2018, approximately half of the total cost for the year. The talks are being held shortly before the arrival of the of US Defence Secretary James Mattis on Thursday. He is scheduled to meet with his South Korean counterpart, Song Young-moo, in Seoul to analyze the current military scenario on the peninsula after the historic US-North Korea summit on Jun. 12 in Singapore Trump and the North Korean leader, Kim Jong-un, signed a joint declaration at the Singapore summit paving the way to the complete denuclearization of the North Korean regime in exchange for Washington providing guarantees for the survival of the North's regime.