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 push aside 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 planned by the end of next year.

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

The U.S. military said many of the recent rocket attacks have come from the Shiite stronghold of Sadr City. On Wednesday, at least two rockets aimed for the Green Zone came from predominantly Shiite areas in Baghdad, the U.S. military said.

The U.S. military says there have been at least 21 rocket attacks — locations firing one or more rockets — in the past 30 days in Baghdad. That compares with 13 in the previous 30-day period.

Sunni insurgents also are blamed for a string of targeted slayings since bombings Sept. 19 that killed more than 30 people in Baghdad — later claimed by an al-Qaida umbrella group.

On Sunday, gunmen using silencer-fitted weapons killed three top officials, including two senior police commanders and an employee of Iraq’s Committee on Anti-Corruption.

Baker said it’s part of al-Qaida in Iraq efforts to “re-establish themselves” in Baghdad and gateways, such as their former stronghold of Fallujah to the west.

“It’s our assessment (that) these attacks are designed to intimidate the public and … create the perception that the Iraqi security forces are somehow weak or ineffectual,” he said.