BEIJING — China has closed Tibet to foreign tourists and deployed soldiers armed with machine guns in the streets of Beijing — part of a raft of stringent security measures ahead of the 60th anniversary of communist rule. Even kite-flying has been banned in the capital.

Although the Oct. 1 commemorations, including a massive military review and speech by President Hu Jintao, are centered on Beijing, the clampdown extends to the farthest reaches of the sprawling nation. Security in the capital is as tight and in some ways even tighter than during last year’s Beijing Olympic Games.

Also, Jintao and President Barack Obama on Tuesday offered each other diplomatic assurances as the U.S. sought help from China in dealing with Iran and North Korea’s nuclear programs at a testy time in ties between Washington and Beijing.

In a meeting on the margins of the U.N. General Assembly, Obama told Hu that his administration regards the nuclear threats posed by both Iran and North Korea as critical dangers to the security of the United States, a senior American official said.