OP's employer is doing what a growing # of employers do. It can be uncomfortable to explain to an employer that you have poor credit and can't really sustain having $1,000 on your card while the reimbursement is processed.

As a first step and before discussing with the employer, I would suggest calling the CC issuer, explaining that you will now be travelling for work and would appreciate it if the issuer would raise your credit limit to acommodate the amounts you will need.

If that doesn't work, you will need to approach the employer. Note that while your card won't be charged before you arrive, that many place a "hold" for the amount of your stay + some % for incidentals at whatever the cutoff for cancellation is.