Let the Battle for Beltran begin. Free-agent slugger Carlos Beltran is in Kansas City being wooed by the Royals, The Post has learned. The club is hoping for a big-bang reunion with Beltran, who began his career in Kansas City. Getting Beltran in pinstripes may be a little more difficult than the Yankees anticipated. Beltran arrived in Kansas City on Monday and is there Tuesday as well to meet with club officials and listen to the Royals’ small-market, big-money pitch. The Royals may be willing to go to three years to sign Beltran. The Yankees would love to ink Beltran to a two-year deal, but Beltran is hopeful of securing a coveted three-year deal, which may be the final contract of his career. The Royals might have to shed payroll, but are making every effort to land Beltran — who turns 37 next April — because they view him as the big run producer they need to reach the next level. Beltran began his career in Kansas City in 1998. He was traded to the Astros during the 2004 season. He batted .287 and compiled an .835 OPS for the Royals, and produced four seasons of 100 runs and 100 RBI in a five-year span from 1999-2003. In Sunday’s Post, Joel Sherman noted the Royals, who won one more game than the Yankees last season, had targeted Beltran because they believe his clutch bat would lead them to the playoffs. The Royals first would need to get some payroll flexibility, and they could decide to deal Billy Butler, who is owed $8 million for 2014 and has a $12.5 club option or $1 million buyout for 2015.