By late this summer, the State Department plans to send dozens of additional diplomatic security agents to high-threat embassies, install millions of dollars of advanced fire-survival gear and surveillance cameras in those diplomatic posts, and improve training for employees headed to the riskiest missions.

The price tag for the security improvements proposed after the attack on the diplomatic mission in Benghazi, Libya, last Sept. 11 has reached $1.4 billion to meet the most urgent needs, including additional personnel. Diplomats and lawmakers say it will take years and billions more dollars to fully carry out the changes called for by an independent review panel that investigated the assault, which killed four Americans. The panel issued 29 recommendations, five of which deal with classified intelligence issues and were not made public.

The department is racing to fulfill the recommendations as threats against United States Embassies in Egypt, Yemen and other hazardous places have sharply increased in recent months. But the department’s ability to correct the security flaws, the financing for it, and the review panel itself, led by the veteran diplomat Thomas R. Pickering, have all come under attack from House Republicans who have seized on the Benghazi issue.

“It remains to be seen how well the State Department implements the board’s recommendations,” said Representative Ed Royce, a California Republican who heads the House Foreign Affairs Committee. “But for any changes to succeed, they must embrace responsibility and accountability at senior levels, which hasn’t happened in this case.”