American carriers will spend slightly more than previously anticipated next year, according to a research note issued this morning from UBS Investment, which upped its 2006 U.S. carrier capex prediction 3%, from $49.9 billion to $51.4 billion.

The new estimate represents an 8% increase in spending from 2005; the old estimate predicted only 4% growth.

UBS made the revision on the heels of the closing of SBC’s acquisition of AT&T, assuming that SBC and Verizon Communications will spend more capital overhauling their newly acquired networks after years of underinvestment by AT&T and MCI.

Spending on U.S. wireline networks should reach $27.2 billion in 2006, UBS said, a 7% increase from its previous estimate of $25.4 billion. Whereas the old estimate predicted 4% annual growth in spending next year, the new estimate reflects 12% growth. That’s twice the growth UBS expects to occur this year.

Ciena, Adtran and Tellabs are most likely to benefit from increased investment in the merged long-distance networks, UBS said, while Nortel Networks and Lucent Technologies—with a high portion of wireless revenue—could benefit least (UBS expects wireless spending growth to slow). UBS singled out Ciena as being in the best position to benefit, since AT&T and MCI have both been significant revenue sources for the vendor.