Yes: in the US, intervening rights can be used for both novelty and non-obviousness rejections.
An example timeline
Let us talk of two applications: P1 and P2, having the following dates:
1 Jan 2015: P1 filed at USPTO.
1 Feb 2015: P2 filed at USPTO.
1 Jul 2016: P1 published by USPTO.
So in a European context, P1 would be novelty-only prior art for P2. But P1 is not full prior art, and therefore could not support an inventive step objection.
The law for prior art
The meaning of prior art is provided in 35 USC § 102(a):
A person shall be entitled to a patent unless—
(1) the claimed invention was patented, described in a printed publication, or in public use, on sale, or otherwise available to the public before the effective filing date of the claimed invention; or
(2) the claimed invention was described in a patent issued under section 151, or in an application for patent published or deemed published under section 122(b), in which the patent or application, as the case may be, names another inventor and was effectively filed before the effective filing date of the claimed invention.
So § 102(a)(1) corresponds to conventional prior art (that is, published before the effective filing date). P1 was published after P2 was filed, and is therefore not § 102(a)(1) prior art.
§ 102(a)(2) corresponds to (what the Europeans sometimes call) intervening rights (that is, filed before but published after the effective filing date). P1 was filed before P2. Once P1 publishes, and assuming P1 names a different inventor, P1 would be § 102(a)(2) prior art. As a practical matter, even before P1 publishes, the examiner may raise a provisional rejection.
The law for non-obviousness
The requirement for obviousness is provided by 35 USC § 103 (emphasis added):
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
Thus the non-obviousness requirement refers back to the prior art definition in § 102 with no further provisos. Accordingly anything which is prior art for § 102 can be used for an obviousness attack under § 103.