* U.S. drawdown in Iraq to pick up pace in June
* U.S. forces to fall to 50,000 by Sept. 1
WASHINGTON, May 11 The Pentagon said on Tuesday the U.S. drawdown from Iraq was on schedule despite this week's deadly bombings and persistent political uncertainty.
The United States aims to withdraw 40,000 troops from Iraq over the next four months -- a major logistical challenge which the Pentagon says will get under way in earnest in June.
The number of U.S. troops in Iraq is expected to fall to 91,000 by the end of May from about 94,000 today and then dramatically drop off to reach a Sept. 1 target of 50,000, Pentagon Press Secretary Geoff Morrell said.
Morrell said he did not believe the pace of the withdrawal during the month of May had been altered because of recent events in Iraq. But he added the top U.S. commander in Iraq had some flexibility as long as the Sept. 1 deadline was met.
A day-long wave of attacks by bombers and gunmen linked to al Qaeda killed more than 100 people on Monday. Morrell acknowledged it was a "horrific day" but said it was an exception to a generally improving security situation in Iraq.
Tensions are also simmering following March 7 parliamentary elections that produced no outright winner.
The U.S. military plans to end combat operations in August and carry out a full withdrawal next year -- more than eight years after the 2003 invasion to topple Saddam Hussein. (Reporting by Phil Stewart; editing by Mohammad Zargham)