* Dollar index rises but is still near 15-month low

* Weak dollar trend to persist, analysts say

* Pound falls after Fitch warns on UK rating

* Euro struggles to hold above $1.50 (Updates prices, adds detail)

By Steven C. Johnson

NEW YORK, Nov 10 (Reuters) - The dollar bounced off a 15-month low on Tuesday and the euro dipped below $1.50 as investors paused to assess whether the global outlook justifies a recent rally in higher-yielding currencies and assets.

U.S. stock indexes were mixed as investors moved to the sidelines, providing respite for the dollar, which investors borrow at low rates to fund purchases of higher-yield assets.

Sterling tumbled after Fitch ratings agency told Reuters that Britain was the economy most at risk of losing its top AAA credit rating, though the pound later recouped most losses.

Analysts said the dollar was still out of favor, though, as investors expect benchmark U.S. interest rates to remain near zero into 2010 as the economy recovers from a harsh recession.