White to move wins with 1 Rg1+ and he will be able to reach the Lucena position.
1...Ra7+
2.Rd7
Ra8
[2...Ra6
3.Ke8+
Kf6
4.e7
Ke6
5.Kf8
wins]
3.Rd8
Ra7+
4.Kd6
Ra6+
5.Ke5
Ra5+
6.Rd5
Ra8
7.Rd7+
Kg6
[7...Kf8
8.Kf6
loses]
8.e7
Kf7
draws *