WASHINGTON — The United States is planning a significant military presence of 13,500 troops in Kuwait to give it the flexibility to respond to sudden conflicts in the region as Iraq adjusts to the withdrawal of American combat forces and the world nervously eyes Iran, according to a congressional report.

The study by the Senate Foreign Relations Committee examined the U.S. relationship with the six nations of the Gulf Cooperation Council — Saudi Arabia, Kuwait, Bahrain, Qatar, the United Arab Emirates and Oman — against a fast-moving backdrop. In just the last two days, Saudi Arabia's ruler named Defense Minister Prince Salman bin Abdul-Aziz as the country's new crown prince after last week's death of Prince Nayef, and Kuwait's government suspended parliament for a month over an internal political feud.

The latest developments inject even more uncertainty as the Middle East deals with the demands of the Arab Spring, the end to U.S. combat operations in Iraq at the end of 2011 and fears of Iran's nuclear program.