"Sanctions should remain in place because lifting sanctions would give the regime precisely what it wants; namely, legitimacy," Republican Senate Minority Leader Mitch McConnell said as he introduced an annual sanctions bill.

The measure, expected to pass easily, includes a ban on importing Myanmar goods, a freeze on US assets held by junta leaders, US opposition to multilateral lending organisations helping Myanmar, and a ban on junta leaders travelling to the United States.

McConnell pointed to two decades of US and UN attempts to engage Myanmars military rulers in a bid to foster democratic openness, and underscored that "none of these efforts has yielded anything in the way of reform."

"The absence of any tangible result from engagement has nothing to do with work of American diplomats. It has everything to do with the type of regime were dealing with in Burma. But again, the fact remains that no progress has been made," said the senator, who represents the state of Kentucky.

His comments came one day after US officials said a senior US diplomat was considering a visit to Myanmar this month amid mounting Western concerns over the military regimes plans for upcoming elections.

The diplomat, Assistant Secretary of State for East Asia Kurt Campbell, is planning to return to Asia for a regional meeting next week in the Philippines along with other stops, US officials said on condition of anonymity.

The United States has voiced concern about Myanmars plans to hold its first elections in two decades later this year, which the opposition is boycotting as it fears they will be a sham by the junta to gain legitimacy.

The opposition National League for Democracy swept the last elections in 1990 but was never allowed to take over. The junta has kept the partys leader, Nobel laureate Aung San Suu Kyi, under house arrest for more than 14 years.

Suu Kyis party has called for voters to shun the poll over rules that would have forced it to expel her as leader if it wanted to participate.

McConnell underlined the juntas moves to sideline Aung San Suu Kyi and accused the regime "trying to stand up a new sham constitution and to legitimise itself in the eyes of the world through a sham election."

"A sanctions regime says to the junta and the world in no uncertain terms that the United States does not view this government as having the support of its citizenry," said McConnell.

"If the regime wants legitimisation, it must show real progress."

Campbell travelled to Myanmar last year as he launched a new policy of US engagement with the country, also known as Burma.

President Barack Obamas administration has made dialogue with adversaries a signature policy and launched dialogue with Myanmar after concluding that longstanding Western attempts to isolate the regime had borne little fruit.

But former political prisoner Aung Din, who heads the US Campaign for Burma advocacy group, voiced concern on Tuesday that a new trip by Campbell could embolden the regimes leader, Senior General Than Shwe.

"Kurt Campbell is coming empty-handed. I want him to go back to Burma with more and more pressure," Aung Din said.