tmsh script modify pool member status

Hi,

I am trying to modify pool member admin status via tmsh script using such command:

tmsh::modify /ltm pool lamp_opi_pl members modify {lamp12_nd:http {session user-disabled}}

but every time script is executed I've got such errors:

pool-status.tcl: script failed to complete:
can't eval proc: "script::run"
members: required brace is missing "{"
    while executing
"tmsh::modify /ltm pool "lamp_opi_pl" members modify {"lamp12_nd:http" {session user-disabled}}"
    (procedure "script::run" line 35)
    invoked from within
"script::run" line:1
script did not successfully complete, status:1

What is wrong with my command? Is that not possible to change admin status for pool member in script?

Piotr