(Reuters) -Canadian National Railway Co said on Thursday it had informed Kansas City Southern’s board about its confidence in winning regulatory approvals for its $33.7 billion offer for the U.S. railroad. Canadian National made an unsolicited bid for the U.S. company on Tuesday, locking horns with Canadian Pacific Railway Ltd and topping the company’s $25 billion bid. Canadian Pacific said on Wednesday it was not considering raising its offer as it did not want put its balance sheet at “risk”. Analysts have said it now depends on which suitor Kansas City Southern wants to go with. Shares of Kansas City Southern were up marginally at $298.51 in morning trading. Canadian Pacific has no overlapping rail networks with Kansas City Southern, unlike Canadian National, making it easier for its deal to clear regulatory hurdles. “We continue to think that what it will all come down to is how the Kansas City Southern board views the regulatory risk of the Canadian National’s proposal relative to the Canadian Pacific deal,” Credit Suisse analyst Allison Landry wrote in a note. An outcome “could ultimately hinge on the shipper response to the U.S. Surface Transportation Board”, Landry said. The U.S. STB oversees freight rail service and rates.