The Obama administration on Tuesday blasted a Republican request for President Barack Obama to send 9,000 troops to secure the border with Mexico, saying it hinders the president's role as commander in chief.

Republican Senators John McCain and Jon Kyl of Arizona, which is facing intense scrutiny over its tough stance on immigration, had requested the National Guard troop increase to help secure the border. Obama on Tuesday had said he would send 1,200 additional troops to the border and seek an additional $500 million from Congress for border security. McCain and Kyl said in a statement Obama's proposal falls short and they wanted 9,000 troops sent instead.

National Security Advisor Gen. James Jones and John Brennan, a top White House counterterrorism official, said the request for 9,000 troops "represents an unwarranted interference with the Commander-in-Chief's responsibilities to direct the employment of our Armed Forces and thus infringes on the President's role..."

Their remarks came in the form of a letter signed to Sen. Carl Levin (D., Mich.), who chairs the Senate Armed Services Committee. McCain is the ranking Republican on the committee and introduced his request as an amendment to legislation before the panel.

Jones and Brennan said a record number of Customers and Border protection personnel are on the southwest border. They said earlier requests from the administration to boost funding to protect and secure the border are yielding results, though more needs to be done. Border agents seized more weapons and cash in 2009 than in the prior year, and violent crime in border states is down.

They said the government's current approach to securing the border, along with working with Mexico, should continue "rather than seeking to deploy an arbitrary number of National Guard personnel."

-By Jared A. Favole, Dow Jones Newswires; 202.862.9256; jared.favole@dowjones.com