The Su T-4 may look like a bastardized version of the US XB-70 Valkyrie bomber, but it was not designed that way. It started out as a response to the SR-71 as a large interceptor that could also serves as a recon platform or a strategic bomber flying at Mach 3!!! The T-4 was a large double-delta with an all-moving plane aft of the large cockpit with drooping nose. It weighed 200 tons and was 170 ft long and powered by 4x Type 57 engines. It could carry 33 tons of bombs to heights above 60,000 ft and cruise with a full load at Mach 2. As interceptor it would have carried two large air-breathing missiles to shoot down the SR-71 and the F-108 Rapier had that fighter appeared with the B-70 over Soviet territory. Only 1 was built and since the XB-70 and XF-108 programs were terminated and the MiG-31 Foxhound would intercept the SR-71, the Soviets used it in 1983 to set 14 aircraft records for payload to height and max speed as "Aircraft 101." It was then retired and sits outside the Monino Museum not far from Moscow. This thing could have appeared over US skies in the 1980s had war broken out and it could outrun the F-15 and F-16 easily. The computer had quadruplex redundancy and it tested FBW systems that helped in the development of the Su-27 family of fighters.

* US XB-70 Valkyrie
** Habu= SR-71 Blackbird
*** Rapier= XF-108 Rapier to accompany XB-70
**** in 1983, the same plane as "Aircraft 101" broke 14 payload to height and speed records
***** Tu-160 Blackjack strategic bomber
The T-4 Sotka:
http://hsfeatures.com/features04/images/t4rj_ref.jpg