How to deal with large number of xml files.

Hello ;

I have several thousands of xml to be sent to a web service from Biztalk. The WS can not handle these amount of XML files. What i need is to slow down the Biztalk on sending these WS requests.

In my orchestration i send xml request to a Web Service and write the
response XML to a file.

Because Biztalk runs asynchronously , it tries to send so many requests to WS. WS can not handle these amount of XML request and crashes down. What can i do ?