diff --git a/fastapi_sso/sso/base.py b/fastapi_sso/sso/base.py
index 1d325a7..8a41d70 100644
--- a/fastapi_sso/sso/base.py
+++ b/fastapi_sso/sso/base.py
@@ -20,6 +20,26 @@
 logger = logging.getLogger(__name__)
 
 
+class HttpxClientKwargsType(TypedDict, total=False):
+    """Parameters of :class:`httpx.AsyncClient`"""
+    verify: bool | str
+    """SSL certificates (a.k.a CA bundle) used to verify the identity of
+    requested hosts. Either `True` (default CA bundle), a path to an SSL
+    certificate file, an `ssl.SSLContext`, or `False` (which will disable
+    verification)."""
+    cert: str | tuple[str, str] | tuple[str, str, str]
+    """An SSL certificate used by the requested host to authenticate the
+    client. Either a path to an SSL certificate file, or two-tuple of
+    (certificate file, key file), or a three-tuple of (certificate file, key
+    file, password)."""
+    proxy: str
+    """A proxy URL where all the traffic should be routed."""
+    proxies: str
+    """A dictionary mapping HTTP protocols to proxy URLs."""
+    timeout: int
+    """The timeout configuration to use when sending requests."""
+
+
 class DiscoveryDocument(TypedDict):
     """Discovery document."""
 
@@ -291,10 +311,11 @@ async def verify_and_process(
         self,
         request: Request,
         *,
-        params: Optional[Dict[str, Any]] = None,
-        headers: Optional[Dict[str, Any]] = None,
-        redirect_uri: Optional[str] = None,
-        convert_response: Literal[True] = True,
+        params: Optional[Dict[str, Any]],
+        headers: Optional[Dict[str, Any]],
+        redirect_uri: Optional[str],
+        convert_response: Literal[True],
+        httpx_client_kwargs: Optional[HttpxClientKwargsType],
     ) -> Optional[OpenID]: ...
 
     @overload
@@ -302,10 +323,11 @@ async def verify_and_process(
         self,
         request: Request,
         *,
-        params: Optional[Dict[str, Any]] = None,
-        headers: Optional[Dict[str, Any]] = None,
-        redirect_uri: Optional[str] = None,
+        params: Optional[Dict[str, Any]],
+        headers: Optional[Dict[str, Any]],
+        redirect_uri: Optional[str],
         convert_response: Literal[False],
+        httpx_client_kwargs: Optional[HttpxClientKwargsType],
     ) -> Optional[Dict[str, Any]]: ...
 
     async def verify_and_process(
@@ -315,7 +337,8 @@ async def verify_and_process(
         params: Optional[Dict[str, Any]] = None,
         headers: Optional[Dict[str, Any]] = None,
         redirect_uri: Optional[str] = None,
-        convert_response: Union[Literal[True], Literal[False]] = True,
+        convert_response: bool = True,
+        httpx_client_kwargs: Optional[HttpxClientKwargsType] = None
     ) -> Union[Optional[OpenID], Optional[Dict[str, Any]]]:
         """Processes the login given a FastAPI (Starlette) Request object. This should be used for the /callback path.
 
@@ -325,6 +348,7 @@ async def verify_and_process(
             headers (Optional[Dict[str, Any]]): Additional headers to pass to the provider.
             redirect_uri (Optional[str]): Overrides the `redirect_uri` specified on this instance.
             convert_response (bool): If True, userinfo response is converted to OpenID object.
+            httpx_client_kwargs (HttpxClientKwargsType): Extra keyword-arguments passed to :class:`httpx.AsyncClient`.
 
         Raises:
             SSOLoginError: If the 'code' parameter is not found in the callback request.
@@ -334,7 +358,7 @@ async def verify_and_process(
             Optional[Dict[str, Any]]: The original JSON response from the API.
         """
         headers = headers or {}
-        code = request.query_params.get("code")
+        code: Optional[str] = request.query_params.get("code")
         if code is None:
             logger.debug(
                 "Callback request:\n\tURI: %s\n\tHeaders: %s\n\tQuery params: %s",
@@ -359,6 +383,7 @@ async def verify_and_process(
             redirect_uri=redirect_uri,
             pkce_code_verifier=pkce_code_verifier,
             convert_response=convert_response,
+            httpx_client_kwargs=httpx_client_kwargs,
         )
 
     def __enter__(self) -> "SSOBase":
@@ -390,11 +415,12 @@ async def process_login(
         code: str,
         request: Request,
         *,
-        params: Optional[Dict[str, Any]] = None,
-        additional_headers: Optional[Dict[str, Any]] = None,
-        redirect_uri: Optional[str] = None,
-        pkce_code_verifier: Optional[str] = None,
-        convert_response: Literal[True] = True,
+        params: Optional[Dict[str, Any]],
+        additional_headers: Optional[Dict[str, Any]],
+        redirect_uri: Optional[str],
+        pkce_code_verifier: Optional[str],
+        convert_response: Literal[True],
+        httpx_client_kwargs: Optional[HttpxClientKwargsType],
     ) -> Optional[OpenID]: ...
 
     @overload
@@ -403,13 +429,28 @@ async def process_login(
         code: str,
         request: Request,
         *,
-        params: Optional[Dict[str, Any]] = None,
-        additional_headers: Optional[Dict[str, Any]] = None,
-        redirect_uri: Optional[str] = None,
-        pkce_code_verifier: Optional[str] = None,
+        params: Optional[Dict[str, Any]],
+        additional_headers: Optional[Dict[str, Any]],
+        redirect_uri: Optional[str],
+        pkce_code_verifier: Optional[str],
         convert_response: Literal[False],
+        httpx_client_kwargs: Optional[HttpxClientKwargsType],
     ) -> Optional[Dict[str, Any]]: ...
 
+    @overload
+    async def process_login(
+        self,
+        code: str,
+        request: Request,
+        *,
+        params: Optional[Dict[str, Any]],
+        additional_headers: Optional[Dict[str, Any]],
+        redirect_uri: Optional[str],
+        pkce_code_verifier: Optional[str],
+        convert_response: bool,
+        httpx_client_kwargs: Optional[HttpxClientKwargsType],
+    ) -> Union[Optional[OpenID], Optional[Dict[str, Any]]]: ...
+
     async def process_login(
         self,
         code: str,
@@ -419,7 +460,8 @@ async def process_login(
         additional_headers: Optional[Dict[str, Any]] = None,
         redirect_uri: Optional[str] = None,
         pkce_code_verifier: Optional[str] = None,
-        convert_response: Union[Literal[True], Literal[False]] = True,
+        convert_response: bool = True,
+        httpx_client_kwargs: Optional[HttpxClientKwargsType] = None,
     ) -> Union[Optional[OpenID], Optional[Dict[str, Any]]]:
         """Processes login from the callback endpoint to verify the user and request user info endpoint.
         It's a lower-level method, typically, you should use `verify_and_process` instead.
@@ -432,6 +474,7 @@ async def process_login(
             redirect_uri (Optional[str]): Overrides the `redirect_uri` specified on this instance.
             pkce_code_verifier (Optional[str]): A PKCE code verifier sent to the server to verify the login request.
             convert_response (bool): If True, userinfo response is converted to OpenID object.
+            httpx_client_kwargs (HttpxClientKwargsType): Extra keyword-arguments passed to :class:`httpx.AsyncClient`.
 
         Raises:
             ReusedOauthClientWarning: If the SSO object is reused, which is not safe and caused security issues.
@@ -451,6 +494,7 @@ async def process_login(
                 ),
                 ReusedOauthClientWarning,
             )
+        httpx_client_kwargs = httpx_client_kwargs or {}
         params = params or {}
         params.update(self._extra_query_params)
         additional_headers = additional_headers or {}
@@ -483,7 +527,7 @@ async def process_login(
 
         auth = httpx.BasicAuth(self.client_id, self.client_secret)
 
-        async with httpx.AsyncClient() as session:
+        async with httpx.AsyncClient(**httpx_client_kwargs) as session:
             response = await session.post(token_url, headers=headers, content=body, auth=auth)
             content = response.json()
             self._refresh_token = content.get("refresh_token")