BGP with ECMP and weight control

[Alexander Demenshin]

Hi,

I have two uplinks (different AS), and one is more stable/preferred,
but when "merge paths" is set to on, all routes are generated with 
weight 1:

5.21.41.0/24 proto bird
         nexthop via 10.16.0.1 dev uplink1 weight 1
         nexthop via 10.17.0.1 dev uplink2 weight 1

Is there any way to adjust weight for ECMP generated from BGP sessions?

I could not find any option/attribute when it is related to BGP or 
kernel
protocol, while it is possible for OSPF and static protocols (to a 
degree).

Adjusting local preference or med (in BGP) does not really help - weight
is unchanged, though of course I could force routes from specific AS
to be preferred, but then I lose ECMP and if preferred session is 
dropped
it takes time to restore connectivity.

Thank you!

Best regards,
Alexander.