BAGHDAD, May 8 — The threat of a walkout by Iraq’s leading Sunni Arab bloc in Parliament and the Cabinet seemed to subside Tuesday after a meeting between Prime Minister Nuri Kamal al-Maliki, a Shiite, and Tariq al-Hashimi, the Sunni vice president.

But Iraq’s violence continued. A suicide car bomber killed at least 16 people near the main mosque in Kufa that the militant Shiite cleric Moktada al-Sadr has used to deliver Friday prayers. It was the third car bomb in a month to explode near a revered Shiite shrine in southern Iraq.

The United States military also announced that two soldiers died Tuesday when a roadside bomb struck their vehicle southeast of Baghdad.

Mr. Hashimi — after threatening earlier this week to lead a Sunni boycott unless there was a clear move to change the Iraqi Constitution so that the country could not be partitioned into separate Shiite, Sunni Arab and Kurdish states — seemed eager on Tuesday to signal progress. His office released a picture of the vice president and prime minister, sitting side by side and smiling, and a statement said the meeting had moved the political process forward.