BAGHDAD – The top U.S. commander for Baghdad warned Wednesday that Iraq’s prolonged political crisis has encouraged militants to step up attacks and left civilians so frustrated they could be holding back crucial tips on suspected insurgent cells.

The assessment by U.S. Brig. Gen. Rob Baker is the most direct link by American military brass between Iraq’s nearly seven-month impasse on forming a government and a recent spike in violence that has included rocket strikes blamed on Shiite militias and targeted killings by suspected Sunni hit squads against security officials and government workers.

Baker’s comments also boost U.S. pressure on Iraqi political leaders to finally pull together after March elections, which were narrowly won by a Sunni-backed coalition but without enough parliament seats to oust the Shiite-led government of Prime Minister Nouri al-Maliki — who seeks to hold on to power.

Vice President Joe Biden called the Sunni bloc leader, Ayad Allawi, on Tuesday to urge a compromise that would satisfy all Iraq’s rival groups. A day earlier, Iraqi Foreign Minister Hoshyar Zebari told The Associated Press that Washington needs to take a more active role in breaking the deadlock.

Baker said he believes Sunni insurgents interpret the political vacuum as a prime chance to undermine the credibility of Iraq’s leadership and security forces and “accelerate” the discontent among Iraqis hoping for a resolution.

“What they will do is try to accelerate that by intimidating the citizens by attacks and by trying to discredit that organization that is trying to protect the citizens, which is the security forces,” he told reporters. “So that is one reason we’ve seen an uptick in the attacks against security forces.”

He also said Shiite militias — some with suspected ties to Iran or loose links to various Iraqi political factions — have recently boosted attacks on U.S. forces and rocket barrages on Baghdad’s protected Green Zone. He attributed it internal Shiite rivalries for “bragging rights” to claim that U.S. forces are departing Iraq under fire. About 50,000 U.S. soldiers remain in Iraq and full withdrawal is slated for the end of next year.

“There’s an intra-Shiite struggle for power … and that manifests itself in violence,” Baker said.