WordPressのリダイレクト処理を教えて下さい。

WordPressにてSSL化して、URLをWWW付きで統一させたいのですがトップページのみwwwナシにリダイレクトされます。
WP管理画面内の設定値はwww付きにしております。
原因がわからないので、アドバイスをお願いします。
ちなみに以下がhtaccessの現状です。

# BEGIN SAKURA Internet Inc.
<IfModule mod_deflate.c>
    SetOutputFilter DEFLATE
    AddOutputFilterByType DEFLATE text/css
    AddOutputFilterByType DEFLATE application/x-javascript application/javascript application/ecmascript
</IfModule>
<IfModule mod_expires.c>
    ExpiresActive On
    <FilesMatch "\.(css|js)$">
        ExpiresDefault "access plus 1 week"
    </FilesMatch>
    <FilesMatch "\.(gif|jpe?g|png)$">
        ExpiresDefault "access plus 1 month"
    </FilesMatch>
</IfModule>
# END SAKURA Internet Inc.

# BEGIN W3TC Browser Cache
<IfModule mod_deflate.c>
    <IfModule mod_headers.c>
        Header append Vary User-Agent env=!dont-vary
    </IfModule>
        AddOutputFilterByType DEFLATE text/css text/x-component application/x-javascript application/javascript text/javascript text/x-js text/html text/richtext image/svg+xml text/plain text/xsd text/xsl text/xml image/x-icon application/json
    <IfModule mod_mime.c>
        # DEFLATE by extension
        AddOutputFilter DEFLATE js css htm html xml
    </IfModule>
</IfModule>
# END W3TC Browser Cache
# BEGIN W3TC Page Cache core
<IfModule mod_rewrite.c>
    RewriteEngine On
    RewriteBase /wp/
    RewriteCond %{HTTP:Accept-Encoding} gzip
    RewriteRule .* - [E=W3TC_ENC:_gzip]
    RewriteCond %{HTTP_COOKIE} w3tc_preview [NC]
    RewriteRule .* - [E=W3TC_PREVIEW:_preview]
    RewriteCond %{REQUEST_METHOD} !=POST
    RewriteCond %{QUERY_STRING} =""
    RewriteCond %{REQUEST_URI} \/$
    RewriteCond %{HTTP_COOKIE} !(comment_author|wp-postpass|w3tc_logged_out|wordpress_logged_in|wptouch_switch_toggle) [NC]
    RewriteCond "%{DOCUMENT_ROOT}/wp/wp-content/cache/page_enhanced/%{HTTP_HOST}/%{REQUEST_URI}/_index%{ENV:W3TC_PREVIEW}.html%{ENV:W3TC_ENC}" -f
    RewriteRule .* "/wp/wp-content/cache/page_enhanced/%{HTTP_HOST}/%{REQUEST_URI}/_index%{ENV:W3TC_PREVIEW}.html%{ENV:W3TC_ENC}" [L]
</IfModule>
# END W3TC Page Cache core
# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
RewriteCond %{ENV:HTTPS} !^on$
RewriteCond %{HTTP:X-SAKURA-FORWARDED-FOR} ^$
RewriteRule ^(.*)$ https://%{HTTP_HOST}%{REQUEST_URI} [R,L]
</IfModule>

# END WordPress