LONDON (Reuters) -Britain's Thames Water, battling to avoid nationalisation, asked a group of senior creditors on Monday to allow it to draw down a further 157 million pounds ($215 million) from the 1.5 billion loan facility that is keeping it afloat.

Meanwhile, the same group of senior creditors are in talks with regulators about their 5 billion pound rescue plan for Thames Water, the only option left on the table for the company to avoid the government's special administration regime (SAR), a form of temporary nationalisation.

Thames Water, which has 16 million customers in London and southern England, issued a statement on Monday asking super senior creditors - the group whose debt holds the highest priority in a company's capital structure - to extend a deadline and waive certain conditions so it can continue to access the loan.

The water utility said on Monday it had so far used 715 million pounds of the initial 1.5 billion loan facility, and said its previous requests for consents to release funds were approved by creditors in April and May.

The government has repeatedly said it is keeping a close eye on Thames Water. Environment minister Steve Reed said on June 19 his department had "stepped up" preparations for SAR.

That came after U.S. private equity firm KKR walked away from a multi-billion pound rescue plan on June 3.

In a rescue deal which would see them take ownership of Thames Water, the senior creditor group has offered new equity and debt and to write off some borrowing, but in return they have demanded looser pollution targets and clemency on fines.

The company was fined 122.7 million pounds in May for breaching its legal obligations over sewage treatment and dividend payments. It will need the consent of creditors to pay that fine, according to the statement.

($1 = 0.7305 pounds)

(Reporting by Sarah Young in London and Yamini Kalia in Bengaluru; Editing by Shailesh Kuber and Ros Russell)