uvm_reg write semaphore

Hello,
Inside uvm_reg there is a semaphore called m_atomic.
This semaphore protect from write/read from several registers at the same time.
I have a sequence that sends an item with write_reg task.
When this sequence is being called several times (different instances) while the write aceess was not finished I can't see the item of the new sequence untill the first one is finished.
I would like to stop the transaction sometimes when the new sequence arrives. How can I do this?
Thanks