Using 'lftp' as a FTPS (not SFTP) client on SuSE Linux ES 11

I have to configure lftp as a FTPS client to be used on a system with SuSe Linux Enterprise Server 11 SP1 installed on it. For that, I have downloaded lftp-4.6.1 and executed following command in order to install it:

./configure --with-openssl --without-gnutls --with-debug

The installation process exits with the following error:

configure: error: openssl development library not found for MD5

I am not able to figure out what package is to be installed so as to remove the error and complete the installation process.

Note: FTPS server is setup using vsftpd.