Pop star Katy Perry. Afp file photo

A US judge kept the door open yesterday for pop star Katy Perry to buy a former LA convent at the centre of an unholy real estate battle, although a final decision remains on hold.

Los Angeles Superior Court judge James Chalfant ruled against the sale of the ex nunnery to a restaurant owner who has been fighting the "I Kissed A Girl" songstress for the right to buy the property.

"There's no doubt in my mind that the sale was improper and invalid," Chalfant said in the latest twist in the legal battle. "It was a bad deal," he added.

But the judge did not rule on whether the Archdiocese of Los Angeles can sell the property to Perry for $14.5 million.

He also said restaurant owner Dana Hollister can remain in possession of the grounds pending a September 15 hearing on whether she, Perry or someone else can best maintain the buildings and provide the best benefits for the nuns.

Hollister was ordered to pay $25,000 a month rent in the meantime. She has not been living on the property but has a caretaker there. She also cannot sell, lease or modify the property in the interim.

The pop singer wants to turn the former convent into her home. The sprawling hillside Italianate complex valued at $15 million is situated near the hip Los Angeles neighborhood of Silver Lake.

But two nuns are having none of it. In a legal salvo last week, the two sisters challenged the authority of the archdiocese to sell the property.

The motion accused the archdiocese of unilaterally changing the bylaws of the convent, known as the California Institute of the Sisters of the Most Holy and Immaculate Heart of the Blessed Virgin Mary.

The suit said that two of the five remaining sisters, who range in age from 77 to 88, were chosen to have "sole authority to amend the institute's bylaws, elect officers and sell the assets of the institute."

Perry has visited the nuns, reportedly singing for them and telling them that she hopes to live on the property with her mother and grandmother.

But the two nuns remain opposed to the sale to Perry, who grew up in a born-again Protestant Christian household but has become both a sex symbol and vocal advocate for gay rights.

Sister Rita Callanan, 77, recently told the Los Angeles Times that she found Perry's videos online and "if it's all right to say, I wasn't happy with any of it."

Callanan and Sister Catherine Rose Holzman, 86, instead signed to sell the property to Hollister. The archdiocese countered that Hollister offered only $44,000 upfront with no promise to make payments to the aging sisters for another three years.

The archdiocese said that the three other remaining sisters supported the sale to Perry. The five sisters no longer live in the former convent, which was once the home to more than 100 nuns.

"The archdiocese is committed to the care and well-being of the Immaculate Heart of Mary Sisters now and in the future," it said in a statement.

"That is our obligation as directed by the Holy See, which will have the final approval over any sale of the property."