Kevin Costner denies any affairs during his marriage to Christine Baumgartner, but 'does not know for a fact' if his estranged wife had any 'extramarital romantic relationships'

• Kevin Costner said he was faithful to Christine Baumgartner during their 18-year marriage.
• Baumgartner's team asked for documents "relating to any extramarital romantic relationships," per multiple reports.

Kevin Costner has denied having an extramarital affair during his marriage to estranged wife Christine Baumgartner — but said he does not know whether the same can be said for her, per court documents obtained by multiple publications.

The "Yellowstone" actor — who, in a recent filing, accused his soon-to-be ex-wife of using "stalling tactics" to delay their divorce — insisted that he remained faithful to his wife of 18 years in response to a request from her legal team as the two sides continue to hash out the financial terms of their separation, a report in People said Thursday.

Entertainment Tonight and People reported that attorneys for the mother-of-three filed new court documents on Monday that included exhibits in which Baumgartner's legal team asked Costner to supply documents pertaining to any "expenses paid by you, or any person at your request or on your behalf, relating to any extramarital romantic relationships."

Costner's legal team responded that the actor "has no responsive documents for 'extramarital romantic relationships' in which he engaged because he engaged in none," said the outlets.

However, per the reports, Costner's team said that the actor "does not know for a fact" if Baumgartner "engaged in any 'extramarital romantic relationships' before separation and, if so, whether she spent any of his money or charged any expenses in furtherance of her affair(s) on credit cards he paid."

The actor's legal team also argued that Baumgartner's request for such documents was "for purposes of harassment," as well as "burdensome" and "oppressive," said the People report.

Lawyers for Costner and Baumgartner did not immediately respond to requests for comment.

Since proceedings began on May 1, when Baumgartner filed for divorce citing "irreconcilable differences," a premarital agreement that the couple signed upon their 2004 marriage has been at the heart of their increasingly contentious divorce.

In July, a Santa Barbara county judge ordered Baumgartner to move out of the former couple's beachfront property in Santa Barbara, per a clause set out in their prenup, and while Baumgartner made good on her promise, she only moved so far as a smaller house on the compound typically used as staff quarters, reported People.

Last month, the couple's child support payment dispute was also settled, with Costner agreeing to pay his soon-to-be ex-wife $129,755 per month until the divorce is finalized — much lower than Baumgartner's original request of $248,000 a month, but still far more than what his legal team proposed.

A hearing to determine the prenuptial agreement's validity has been scheduled for November.