By Chuck Mikolajczak
NEW YORK (Reuters) - U.S. stocks were poised for a flat open on Friday, as futures pared losses after the latest flare of tensions between Ukraine and Russia, and ahead of a speech by Federal Reserve Chair Janet Yellen.
Futures initially lost ground after Ukrainian authorities said trucks from a Russian aid convoy had crossed into Ukraine without permission, which it termed a "flagrant violation" of international law and as the country appealed to the international community to condemn Russia's actions as illegal and aggressive.
Market participants will closely monitor a speech Yellen is due to make at a policymakers' meeting in Jackson Hole, Wyoming, for insights into how soon interest rates may be raised. European Central Bank President Mario Draghi is also expected to speak.
The S&P 500 <.SPX> has risen for four straight sessions, its longest streak in two months, rallying to a record closing high of 1,992.37, on positive economic data. The benchmark index is up 1.9 percent for the week, on track for its best week in four months.
S&P 500 e-mini futures
Foot Locker
Aeropostale
GameStop Corp
Peregrine Semiconductor
(Editing by Bernadette Baum)